1. From your main dashboard, select “Contacts” on the top toolbar.
2. Select the names you want to add or remove Tags from by clicking the check box in front of the name or by selecting the whole list by clicking the check box above the word “Temp.”
3. Click on “Manage Tags” on the right side under Actions for Selected. 
4. To add a tag, begin typing the tag word into the “Add Tags” box and select it from the dropdown. If you have used this tag before, it will appear in the dropdown, and you can select it. If the tag is new, click “add to list.”
5. To remove a tag, begin typing the tag word into the “Add Tags” box and select it from the dropdown. If the tag is new, click “add to list.”
6. Once you have selected which tags you wish to add and remove, click “Add/Remove These Tags” below.
See the CRB Training Manual for more information: p. 18
https://cssagent.com/uploads/documents/Marketing_Prospect_System_Manual_Cornerstone_v4.pdf#page=22