“Tagging” locations can be done one of two ways. The informal method is to use free-form tags that are setup via the Power add on. The structured method is to use the Category Manager under the Categories tab which you will see when you have the Power Add-on Installed.
The Categories Manager is almost-always the better solution. It uses the WordPress taxonomy system to link categories to locations. It supports hierarchical category structures and allows map markers and icons to correlate to the category. It is the best way to assign custom map markers and icons to locations for things like “services provided” or products.