My wife and I love this hike and come up here once or twice every year.
The cache is about 3 miles of uphill hiking from the car parking on the Guanella Pass road or if you have a decent vehicle you can drive about 2/3 miles closer and park at the trailhead.
Take the trail until you are within a couple hundred feet of the cache and then walk over to a big rock for your search. Elevation will be around 12,180'