Go to the people tab on the left hand side under the “General” heading

Select one or more People or search for specific People using filters/advanced filters

Once you have your group selected, the quick action bar will pop up along the bottom of the screen

Click the “Manage tags” icon (small tag)

Toggle between “add” or “remove” depending on desired action.

Next you will type in the tag you wish to add or select from the drop down menu. Be sure to click the word that populates below if this is a new tag.

Then select “update”