Parked in the large entranceway on the road above the village of Owning (Onainn, as gaeilge). There is an old mill/workhouse at the end of the track here. Walk to the right around the back of the adjoining house and the ruined tomb is in the 2nd field on your left.
It's quite a sad sight, with the slipped capstone resting on the collapsing uprights. The day I was there (19/08/06) I noticed that some chemical weedkiller had been used on the brambles etc. but the resultant burnt foliage hadn't been cleared and new growth was in evidence. There's work going on around the tomb and maybe when the 'important' stuff is done, they'll finish clearing up the tomb.