Your Apple Watch takes data from your iPhone and shows it to you on its screen. If you want to sync your iCloud data (contacts, calendar, and email), sign in with your Apple ID, either during the initial setup or using the Apple Watch app on your iPhone. Watch-compatible apps can be transferred from your phone to your watch, which will sync their data as long as your phone is nearby.
Steps
Part 1 of 2: Pairing the Watch

Step 1. Update your iPhone
To get the most out of your Apple Watch, you should have the latest version of iOS installed on your iPhone. The Apple Watch app will only appear if you are using iOS 8.2 or later on iPhone 5 or later. To update your iPhone, go to Settings > General or connect your iPhone to your computer and open iTunes.
Read this article to know how to update your iPhone

Step 2. Turn on Bluetooth on your iPhone
Apple Watch will connect to your iPhone via Bluetooth, which is why you need to activate the Bluetooth module on your phone. Swipe up from the bottom of the screen and tap the Bluetooth button to turn it on.
Your phone must also be connected to the Internet, whether over Wi-Fi or through a cellular network

Step 3. Open the Apple Watch app on your iPhone
If you're using an iPhone 5 or later that runs iOS 8.2+, the app will be on one of your Home screens. If you cannot find the application, it means that your iPhone does not meet 1 or these 2 conditions.

Step 4. Turn on your Apple Watch
Long press the button under the wheel on the side of your watch. Apple Watch will start the setup process on startup.
Select your language using the touchscreen or the wheel on your watch

Step 5. Tap Start Pairing on the watch and phone
A pattern will appear on your watch screen and your phone's camera will open.

Step 6. Point your phone's viewfinder at the screen of your watch
The watch should be in the center of your screen. If it is properly aligned, you will feel it vibrate quickly.
- If you can't pair your devices using this method, tap Pair the Apple Watch manually. Select your watch from the list and then enter the code displayed on its screen into your iPhone.

Step 7. Tap Set up Apple Watch on your iPhone
Apple Watch will be set up as a new device and you can sync content from your phone.
If you've used an Apple Watch before, you can restore it from a backup that will be downloaded from iCloud

Step 8. Select the wrist you will be wearing the watch on
This step allows the sensors to be calibrated. Choose the non-dominant hand so that you can operate the watch with the other hand.
- To select the wrist you will use, press Left Where Law on your iPhone.

Step 9. Log in with your Apple ID on your iPhone
This step is not mandatory, but it will give you access to more advanced features of Apple Watch (such as Apple Pay, which allows you to pay with your watch in appropriate stores). Make sure you sign in with the same Apple ID you used on your iPhone.

Step 10. Create an access code for your watch
In the event of theft, this measure will prevent all access to your watch. You will be asked for the code when you put it on and take it off. You don't have to create an access code.
You will also be asked if you want your watch to unlock at the same time as your phone

Step 11. Install apps that are compatible with your watch
You will be prompted to install all available apps right away or wait for the next time. Your Apple Watch cannot download and install apps from the App Store. However, you can install compatible applications directly from your phone. This step also synchronizes app data with your watch.
If you don't want to install all the apps at once, skip to the next section for how to choose which apps to sync

Step 12. Wait for your Apple Watch to sync with your iPhone
Synchronization of your watch will begin after you choose whether or not to install all of the available applications. If you choose to install them later, it will sync quickly, but if you install all compatible apps, it will take some time. You will receive a notification when the synchronization is finished.
Part 2 of 2: sync content

Step 1. Log in on your watch with your Apple ID
The information stored in your iCloud will be synced (contacts, calendars, email accounts, and favorite iCloud photos). You can only sign in with one Apple ID at a time. If you didn't sign in during the initial setup, you can use the Apple Watch app on your iPhone.
- Open the Apple Watch app on your iPhone.
- Go to the tab My watch at the bottom of the screen and select General.
- Press on Apple ID then sign in with your Apple ID. Your iCloud data will sync from your iPhone to your watch, which may take some time. If you have more than one Apple ID, sign in with the one you're using on your phone so you can use it on your watch.

Step 2. Transfer apps and data from your iPhone
Signing in with your Apple ID not only syncs your iCloud information, it also transfers compatible apps from your iPhone to your watch. You were prompted to install them all at once during the initial setup, but you can choose which apps to display using the Apple Watch app on your iPhone.
- Open the Apple Watch app and select My watch at the bottom of the screen.
- Scroll down and tap the app you want to add or remove from your watch. Only the apps installed on your iPhone that are compatible with your Apple Watch will be displayed.
- Activate or deactivate the option View the app on Apple Watch to find out if the app is installed on your watch. The process may take some time and the application data remains fully managed by iPhone.

Step 3. Sync your music with your watch
Normally, Apple Watch only acts as a remote control to listen to music on your iPhone. However, you can sync a playlist with to listen to it without your phone if you pair it with a Bluetooth headset. The playlist will need to be created on your iPhone.
- On your iPhone, open the app Music and create a new playlist. Your watch can store up to 2 GB of music (approximately 200 songs). All the songs you want to add must be in a single playlist.
- Connect your watch to its charger and make sure your iPhone's Bluetooth is turned on.
- On your iPhone, open the Apple Watch app and select My watch at the bottom of the screen.
- Press on Music then on Synchronized playlist. Select the playlist you want to sync with your watch. The duration of the process will depend on the amount of songs transferred and the synced list will only be visible if you have a Bluetooth headset paired with your watch.