Moth - it is a difficult one to find, if I remember rightly (it's over a year since I visited)...

Approaching from the East, the road bends to the right as it starts to descend the hill. To the right there is a track leading down to Grimwith Res. (Grimwith Road). Park up here (don't go down the road to the res.) I'm not sure if parking is really permitted, but I did anyway - I think there's just about enough room to pull in without obstructing the complicated series of gates. Don't go down the track, instead vault the gate into the field to the right of the Grimwith Road. Head up the field following the wall between the field and the main road. Once you come to another field wall, start to follow this up the hill and the circle will come into view on a flat section.

This is all off the top of my head, based on what I can remember. Fitz might be able to offer up more clues.

I did have a bit of trouble finding it to be honest, and had been trudging around the field below for a while before deciding to head up the hill... so, as a wise Welsh farmer once said to me as I was trying to find Din Dryfol, just follow your nose! :-)