If you need to disable one of your users follow the next steps.
Go to your Settings and select "Users" from the top menu. Then select the user you wish to disable.
When the user's profile pops up, select the option to disable on the bottom of the screen. You will get a pop up asking if you're sure, click "Yes, Disable user!". This will be followed by an alert indicating that the changes have been made.
This user will be temporarily disabled and will not be able to be used by anyone unless it's enabled again.
If you wish to enable that user, follow the same steps to get to the user's profile and you will have an option to "Enable" user instead of disable. Click on it and then select "Yes, activate user!" on the pop up. This will be followed by an alert indicating that changes have been made.
Please don't hesitate to contact Support if you need further assistance.