Locations are used for proximity-based Project requirements. For example, "within 25 miles of New York, NY 10018".
Add Location to Members
Click the Add Address button on Org Setting > Members > Location.
This provides two options:
Select one of the created Offices
Add a custom Location
Click Create to add work address for the member
Modify Locations
Click on the work address of the member
You can modify the custom address, select a office as the work address or delete this address