You cannot change your username.
When you sign up, make sure you come up with a username you like.

But you can change your email. Send us a request to [email protected] from the email you initially registered. In your request, write your new email. We can also fix typos in the email linked to your LiveXP account. Just message us in the Support chat to request the edit.

NOTE: if you entered a non-existent email during registration, unfortunately, nothing can fix that. 

In this case, you need to create a new account with an existing email and inform Support about your first account. We will delete the account with the non-existing email.