GCC Verdugo Library is located next to the Student Center, which is around the corner from the Welcome Center.
It is a round building you can see once you get off the elevator from the C Parking Lot/Building.
From your class in the auditorium, you can cross Plaza Vaquero, go up the stairs by the fountain, and walk right up to the front door of the library.
Here is a map of the campus with the library circled: