1. Go to the user management page.
2. Select the user of interest by placing a tick in the tickbox to the left on the row that his name appears.
3. Click on 'bulk edit roles' at the bottom of the page.
4. Select the the role you want to give the user in the location and department of interest.
5. Click on 'Apply'.
Should you be having trouble trying to bulk edit roles with many users, try selecting one user at a time.