You can see the trailhead at the dead-end (88 Farnsworth on Street View), but the trail has no signage except to say you're now entering UCSF property. This is just past the swing (pic 5).
Once on it (pix 6, 7), just continue south to this short trail's dead-end and cross the Surge parking lot to access the other trails. I've done this for years.
On Medical Center Way's guardrailed walkway (8 thru 12), including a view down to the Fairy Gates Trail (pic 13), it's a vigorous uphill hike to the East Ridge Trail (pic 14) whose foot is across from the Aldea Center.
What a difference the rains have made with all the new spring leaves and muddy trails. Mere photos can't adequately describe the fresh aroma and damp bark of the trees up here.
Out at the summit (pic 15) for lunch at the benches (pic 16), then onto the North Ridge Trail, 17 thru 25, past Ishi's shrine and back down to Medical Center Way.
Crossed the parking lot once more (this time took the 47 steps down outside one of the medical buildings), then the 136 steps down to lower Medical Center Way (off Parnassus), last six pix. Partway down, a short old wood stairway climbs to the aforementioned unnamed trail behind the homes.