Guide

1. Head over to the gear icon on the top right.

2. Select Setup from the dropdown.

3. Look for Users under ADMINISTRATION in the left pane.

4. And select Users.

5. Make sure the View dropdown says All users.

6. Click on Edit on the left column.

7. The User Edit screen will open and you will see the Active box checked.

8. Uncheck Active box.

9. Clicking on the Save button at the bottom.

10. You will now see your selected user without the checkmark.

    This means the user's access to Salesforce is now deactivated.