Step 1.) Click on 'Locations'
Step 2.) Click on the checkbox at the top to select all locations
Note: To add a tag to only one location just click on the checkbox next to a specific location.
After clicking on the checkbox at the top, this will select all locations as shown below.
Step 3.) Click on 'Tag' at the bottom.
Step 4.) Click on 'Create New Tag'.
Step 5.) Enter the tag in the space provided, and click 'Save'.
You're all done!