Whether you're coming from Southern California, Northern California, or out of state, sooner or later you're going to get on Scenic Califonia State Highway 198, which is the only way to get to Three Rivers.
Once you're in town, look for the Chevron Station. About 100 feet past the Chevron station is a little blue sign on the left side of the road that says LIBRARY. You're at Eggers Drive. Turn RIGHT and head up the hill till the road T's at Mynatt. Turn RIGHT on Mynatt, go about 100 feet and look for the third driveway on your left. The address is 42182. (If the driveway isn't steep and scary you're in the wrong place.) Drive on up and look for signs for Guest Parking. Follow the signs to walk around to the front to check in.