The widdershins trailhead is directly across the road from the Wawona Hotel, which you can see by clicking on the picture and rotating it 180 degrees. (If the panorama view you're seeing doesn't include a golf cart, you might need to rotate it anyway; Google Street View is occasionally a little buggy.) The trail starts on the other side of the golf course; if you're seeking the trailhead from this spot, get out of the road with all possible dispatch, then walk past the golf cart to the trees and turn left.
The clockwise trailhead starts about a quarter mile east of the hotel; it's shown below. You're allowed to pull in and park here.