You cannot change the username associated with your Snapchat account. However, you can delete your current account and create a new one with a different username. You can also change your nickname, which is the name other users see when you communicate with them.
Steps
Method 1 of 3: Delete your old Snapchat account

Step 1. Open Snapchat
Tap the yellow ghost icon to launch the app.

Step 2. Open your account
Swipe down anywhere on the screen to view your Snapchat account page.

Step 3. Press the ⚙️ icon
This icon is located at the top right of the screen and opens the settings menu.

Step 4. Tap Support
Scroll down the menu and tap Support in the 'More Information' section.

Step 5. Select My Account & Settings
This is the last option at the bottom of the screen.

Step 6. Select Account Information

Step 7. Tap Delete my account
Select the Delete my account option in the middle of the menu. You will be taken to a new page explaining how to delete your account.
If you want a new username, but don't want to delete your current account, you can just create a new account

Step 8. Tap the page link
It's in the second paragraph.

Step 9. Enter your password
You must do this to confirm that you want to delete your account.
If your username does not appear automatically, you will also have to type it

Step 10. Select Continue
Your Snapchat account is now deactivated and will be deleted after 30 days.
- If you change your mind, you have 30 days from the time you deactivate your account to reactivate it by logging into Snapchat with your credentials.
- Since February 2017, it is not possible to transfer your friend list to Snapchat. You should find most of them in your device's contact list, but it is advisable to take a screenshot of your friends list before deleting your account.
Method 2 of 3: Open a new account

Step 1. Launch Snapchat
Select the yellow icon containing a white ghost.
If the connection is not automatic, type your username and password

Step 2. Swipe the screen
Slide your finger down anywhere on the screen to access your user page.

Step 3. Press the ⚙️ icon
It is located at the top right of the screen and opens the settings menu.

Step 4. Log out
Scroll down and select Logout at the bottom.

Step 5. Tap Sign Up
This will allow you to create a new Snapchat account.

Step 6. Enter your name
Type your first and last name in the corresponding spaces.

Step 7. Select Validate and Accept
Then type your date of birth in the corresponding space and press Next.

Step 8. Enter your new username
Choose the name you want associated with your Snapchat account.

Step 9. Type your email address
It must be different from the one for your old Snapchat account.

Step 10. Follow the rest of the directions
From this point you can skip any steps you want and add new or old friends from your contact list.
- Once you have created your account, you can change your email address and phone number from the Settings menu.
- You can delete your old Snapchat account or keep it if you think you will use it again in the future.
Method 3 of 3: Change your nickname on Snapchat

Step 1. Open Snapchat
Click on the yellow icon containing a ghost to launch the application.
If the connection is not done automatically, enter your username and password

Step 2. Open your account
Swipe down anywhere on the screen to open your account page.

Step 3. Click on the ⚙️ icon
It is located at the top right of the screen and provides access to the Settings menu.

Step 4. Tap Name
This is the first option at the top of the menu.

Step 5. Enter your new nickname
You can enter a simple first name or a first and last name. Pick something that your friends can easily recognize.
If you do not want to have a nickname displayed, click Remove name. Other users will then see your username, but if it doesn't identify you, your friends will have a hard time finding you

Step 6. Tap Save

Step 7. Return to the menu
Click on the arrow at the top left of the screen to return to the main menu. Other Snapchat users will now see the name you just typed when you send them Snaps or post a Story.