The trailhead is very easy to access as it is just off Highway 80 at the Boreal Mountain exit. When taking the exit, take a turn to the North, rather than to Boreal on the South side of the Highway.

On busy summer weekends this trailhead can get quite crowded so you may have to park at the bottom of the road less than 100 yards from the Highway 80 off-ramp. The first mile of the trail is actually a forest road and you can take your 4x4 further up if looking to shorten your hike or even car camp in the National Forest. 

From the trailhead to the Peak is about 3 miles and the trail is well maintained so easy to follow. The first couple of miles head Northwest on a gradual slope until you reach Castle Pass, which junctions with the Pacific Crest Trail. Once on top of this pass, follow the Castle Peak ridgeline to the Northeast. After about a half mile along the scenic ridge the trail will become steep as it wraps around the northern slope of the mountain until you reach the actual peak. It's pretty obvious to follow since the south face of the mountain is made of sheer rock cliffs. Be careful of loose rocks when reaching the summit.