There's impressive views of the ridge that includes Slieve Snaght and Dooish as well as Errigal and much of the rest of Donegal such as the Bluestacks from this summit.
One easy way to ascend is from the NE, starting at around B9616 1492 A on the R254. There is a small battered bridge here and various places to park. Go SW to reach the summit, savouring the widening view as you ascend. The height gain is around 330m to the top and a round trip will take perhaps 90 minutes.
Another place to start is from the car park beside Lough Barra at B936124 B. The route is approximately NE from here, requiring finding a place to cross the river Barra. This may not be possible after heavy rainfall. Linkback: https://mountainviews.ie/summit/377/comment/5136/

Climbed 20.11.05, parking at layby next to Lough Barra (936124 B) on the beautifully scenic R254. I followed a track on the other side of the road to the shore of Lough Barra and walked its sandy shore to the mouth of the River Barra, having to follow it inland to find a crossing point on one of its turns. There is some pretty wet ground to cross before the ground turns rockier as begin to climb. Even from here there are breathtaking views across the valley to Slieve Snaght and her companions. As gained height the line of the Bluestacks came into view behind Aghla Mountain, with the higher tops capped in cloud. There is a cairn at the top and the views extend to Errigal, Macknoght and the Aghlas - beyond the immediate and imposing line of hills from Dooish to Slieve Snaght. Head nearly due N for another small small cairn with views across the deep valley below which extends to the head of Glenveagh, with glimpes of the lake. Drop down NE along the steep face of Moylenanav where the ground is again pretty wet, can eventually drop off the hill to acess the road and follow it for 30 minutes back to the layby beside Lough Barra. I first saw this hill from across the valley on the Bingorms and it looked a good hill, it lived up to those thoughts and provided a few hours of walking along lough, river and hill, with stunning views on a fantastic day with clear blue skies - what more could you ask for? Linkback: https://mountainviews.ie/summit/377/comment/2066/

Walking up the NE slope of Moylenav allows a succession of keyhole views through the Slieve Snaght - Dooish ridge. In this picture Errigal, particularly jagged from this angle, is seen through the gap between Crockfadda to the right and Drumnalifferny Mountain to the left. Linkback: https://mountainviews.ie/summit/377/comment/6094/

My wife and I climbed Moylenanav in April 2005. We started from the R254 at the back entrance to Glenveagh (MR B971158 C). We walked SW up the road for about 1k to a small bridge over a stream and turned left to initially follow up stream before heading SW up the shoulder of Moylenanav. There is a small cairn located at the N end of the summit plateau with fine views across to Slieve Snaght and through a gap in the ridge to Errigal. From here it was a short walk SE to the summit cairn at 539m. The views were extensive. To the SW Slieve League, Slievetooey and the long ridge of the Bluestacks were clearly visible. From the top we descended SE to a coll before climbing briefly to the broad flat top of Crockskallabagh, which is covered in peat hags and lacks a clearly identifiable summit. To avoid descending the steep and rocky NE slope we headed NNE in the direction of Meenbog Hill which we had intended to climb on our round. At the base of Crockskallabagh we found the going increaseingly marshy and decided to head NW to pick up the stream we had started at and walk down to the road. We turned right at the road and walked back to the car. We enjoyed this short but satisfyiny walk and would commend it to those looking for something different in the Derryveagh Mountains. From start to finish we encountered no fences or any other obstacles apart from wet and marshy ground on the walk back to the road. Linkback: https://mountainviews.ie/summit/377/comment/1778/

Approached Moylenav from Glendowan Beg area taking track (waterlogged in places) via minor top of Croaghnagapple, descending to head of Sruthangarrow and onto Croaghcullin & Crockscallabagh before short ascent to Moylenav's summit. Excellent views all around from Crockscallabagh onwards. Moylenav provides tantalising views of Bingorms sheer cliff-face & Sliabh Snacht across the R254. However, my route on the day took me down into the boggy valley leading to Meenabog Hill. One can't help but feel that the Anglicised name for this hill provides a better description of its topography than its true Irish meaning. I was glad to get off it and across the road to continue circuit via Farscallop & An Liathan Mór. Linkback: https://mountainviews.ie/summit/377/comment/3071/

Climbed Moylenanav by the route described by Harry Goodman and a fine day it was too, the promissed sunshine had arrived along with temps in the mid twenties. The thought of dried out bog spurred us on to include Crockastoller in our circuit for the day. Hot and sunny it was, dried out bog it wasn't! See Glendowan Mountain Circuit in the walks section for the details. Linkback: https://mountainviews.ie/summit/377/comment/5817/