To access the trails, head south on Highway 191 out of Blanding, then head west onto Highway 95. Once you've past mile marker 84 on Highway 95, you'll come to State Road 276.
To reach the Moki Canyon Trails, take 276 until mile marker 63, at which point turn onto County Road 2221. Just prior the the Sand Slide, you can elect to either head east to continue along the Moki Canyon Trail, or head west to the Lower Moki Canyon Trail.
To reach the Castle Wash Trail, follow the same directions, but look for mile marker 60 on 276, where you'll see a sign for ATV Trail 96.