You can configure ClickTime to give users access to a specific list of sites.  

Each user that is defined in WorkTimeManager can be assigned to have full access to all sites & jobs or to only have access to a particular set of sites & jobs.

In order to restrict users to a specific set of sites & jobs, follow the below steps:

1- Go to Settings → Users & Permissions

2- Click & select the user record

4- Click and navigate to the Assigned sites/Teams tab

To grant the user access to all sites

Make sure to tick the Allow user to view & work with all sites and jobs to YES

To grant access the user access to only a particular set of sites & jobs, then

A. Make sure to tick the Allow user to view & work with all sites and jobs to NO:

B. The system will display & show Available Sites & Jobs to the left side of the screen and Assigned Sites to the right side of the screen

C. Drag & drop the sites & jobs from the left side to the right side or double click on the record to be assigned

To the user.