Locations: Custom Attibutes

I'm trying to find where I am able to create custom attributes for Locations in the sandbox.  I can see that somebody has already created a custom attribute for locations called "On-Campus."  I'd like to create some more attributes, particularly for rooms, which denote whether the projector video connection is digital or analog, what model the projector in the room is, etc.  I have admin access in the sandbox.  I see that I have all kinds of access to attributes in the assets application, and I can create locations.  But I am not able to create or modify attributes for locations.