There is a large parking area next to the highway. A trail leaves the parking area at the east end (towards town) and goes to the Killer B trailhead.
If you are southbound on Highway 191, the parking area is on the left, just past the end of the divided highway and just before a sign reading "Slow Traffic Keep Right."
Killer B is primarily a mountain biking trail. It looks and is intimidating, which is probably how it got its name. At the top it connects to numerous Bar-M bike trails and is typically used as a downhill route from those other trails. You can hike it if you want, but watch for bikes as they come down fast. Geocachers don't have to hike the trail. At the trailhead sign you can leave the trail. The cache is about 400 feet from the parking area, and contains swag, and for one person a FTF coin.