To add a new user, click the Add User button and fill out the form fields on the screen.
To re-enable a user previously disabled, click on that user's name followed by the Enable button and choose an appropriate access level.
To remove a user, click on an existing user's name followed by the Disable or Delete buttons. Disabling a user will retain all of that person's historical information entered in CATS. Deleting a user will allow you to map all of their activities to another user. Both disabling and deleting users will remove them from your monthly cost.
For questions regarding the different user access levels, please refer to this article.