It's easy to add friends on Facebook by sending or accepting friend requests on your computer or mobile device.
Steps
Method 1 of 2: Submit a request
On mobile device

Step 1. Open Facebook
It's a dark blue icon with a white "f" in it. This should open your Facebook account newsfeed if you're signed in on your phone or tablet.
If you are not logged in, you will need to enter your email address (or phone number) and password before continuing

Step 2. Tap on the search bar
You will find it at the top of the screen.

Step 3. Find the friend you want to add
Type its name, then select it from the drop-down menu that opens below the search box. This should bring you to his profile.
You can also tap their name in your news feed to open their profile

Step 4. Select Add Friend
It's a silhouette icon that can be found just below the person's profile picture. This will send him a friend request. If he accepts it, he will be added to your Friends list.
On computer

Step 1. Go to the Facebook site
Go to https://www.facebook.com in the browser of your choice. This allows you to see your news feed if you are already logged in.
If you are not logged in to Facebook, you will need to enter your email address (or phone number) and password before you can continue

Step 2. Click on the search bar
You can find it at the top of the page. This is where you go to find the person you want to add to your Friends list.

Step 3. Find the name of the person to add
Type in its name, then click the corresponding option in the drop-down menu that opens. This will bring you to his profile.
Alternatively, you can also select their name in your news feed to view their profile

Step 4. Click Add Friend
This is the button to the right of his profile picture, click on it to send him a friend request. If he accepts it, he will be added to your Friends list.
Method 2 of 2: Accept a request
On mobile devices

Step 1. Open Facebook
It's a dark blue icon with a white "f" in it. This will open your Facebook account news feed if you are logged in on your phone or tablet.
If you are not logged in, enter your email address (or phone number) and password to continue

Step 2. Tap ☰
You will find it at the bottom right of the screen (on iPhone) or at the top right of the screen (on Android).

Step 3. Select Friends
This option is near the top of the menu.

Step 4. Tap on Friendship Requests
You'll see it near the top of the page.

Step 5. Select Confirm
This is the blue button that appears under the name of the person who sent you the request. Tap on To confirm to accept the request and add that person to your Friends list.
On computer

Step 1. Go to the Facebook site
You can find it at https://www.facebook.com in your browser of choice. This allows you to access your news feed if you are already signed in.
If you are not logged in to Facebook, you must enter your email address (or phone number) and password before you can continue

Step 2. Click the Friends icon
It looks like the silhouettes of two people and can be found at the top right of the page. This will open a drop-down menu.
If you've received a friendship request, you should see a white number on it with a red background next to it

Step 3. Click Confirm
It's a blue button under the person's name. Clicking on it will accept the request and add that person to your Friends list.