We don't currently offer the ability to change your username within data.world, however, there are a couple of workarounds:
create a new account using a different email address. If you'd like the initial account removed once you've created your new account, just submit a request for us to do so. Once removed, you could then go into your account settings to update your email if desired.
submit a request for us to delete your account which will free up your email address so you'll be able to create a new account with the preferred username.
Note that both of these options will remove all content and social activity (likes, follows, etc.) associated with the account being deleted. Please be sure to back up your work and be ready to recreate it under the new account.