To change your username, email, or password, please go to your Settings from either the drop down under your username and profile picture, or on the side bar.
You can change your username one time only, from your Settings. Just scroll to the "Username change" section, and enter your password. You will then be able to pick a new username.
One thing to note: your old name will always refer to your account. You'll be able to log in with either your old or new name. This means that nobody will be able to impersonate you by taking your previous name. quizlet.com/jalenack and quizlet.com/asuth are the same user.
If you log in to Quizlet with Facebook, you'll be asked to verify your Facebook account before you can change your username:
Email address and Password
On the Settings page, you can change your email or password: