UCLA's home page maintains a useful set of instructions and maps for reaching campus via the local freeways (if you're arriving by car) and by bus.
Here's how to reach the Physics & Astronomy Building. The closest parking structure to the Physics & Astronomy Building (PAB) is Structure 2. To park, you'll need to stop at the parking kiosk just inside UCLA at the corner of Hilgard Ave. and Westholme. UCLA Parking accepts cash payment at the kiosk ($12 per day), although there are some pay-per-space areas in Structrure 2 that accept credit cards.
Please note these summer traffic alerts that may affect your travel to UCLA.