The user configuration page can be accessed via the Configure button in the top left corner and then selecting User Configuration.
To remove a user, select them from the list and click Remove. Then click Save.
When you Add a user, you insert an email address and click Next. Then you enter their full name and click OK.
Select the new user from the list and give them privileges (see User Configuration for more details on how privileges work). Finally, click Save and the new user will receive an email and can start using exTables.