To define common event locations, navigate to your side bar and click 'Settings', then click 'Locations'.

Location Listings - Summary 

+ Use the 'Add' button to add a new location listing.  This will be available for your default campus.
Magnifying Glass Use the 'View' button to view the Full location details.
Edit Use the 'Edit' button to edit an existing location or to change the 'Campus' it belongs with.
Trash Can  You can delete locations with this button so they will no longer be available in the pick list for events.