Account Owner and Manager user accounts can delete other user accounts.
To delete a new user, navigate to the Users page via the Settings menu in the upper-right part of the screen.
Check the box next to the user accounts you wish to delete, please note that there is no checkbox next to the user account you are currently logged in as. If you wish to delete the account you're logged in as, you'll need to log in as a different user. It is not possible to delete the Account Owner account:
Click on OK in the Confirmation Dialog popup:
The user has been successfully deleted: