Park at the forestry entrance W13673 54386 A, room for 2-3 cars. Walk uphill on a generally good forest road to the summit. As mentioned by thomas_g there are " you are on a farm signs" a little way along this track but they seem to point both ways , I took them to possibly refer to an access track between them , a distance of less than 100 meters. Also there is a standard Coillte rules of access sign at the start of this track so access should be fine.
the summit is a mess of bulldozed ground, portacabins and aerials. Linkback: https://mountainviews.ie/summit/384/comment/5143/

The Mealagh valley sign marks where I parked at W137 544 B (room for 6 cars), it's like the valley that time forgot and feels very isolated. There is a forest road all the way to the summit, which starts out level and gets steep at the end. The ascent doesn't offer much in the way of views, but the views to the south must be stunning on a clear day, if you can forget all the masts.
I'm wary about the access, I noticed some of the standard "you are on a farm, no un-authorised entry" signs about 1/3 the way from the car. They appear to point in both directions, so I'm a bit unsure where you can't enter, but there are possible access problems via this route.
I had intended to bag another Arderin by walking the 1.5km to Nowen SW, but the terrain looked truly horrible, tussocky grass with bog between the tussocks, I'll keep that treat for a drier day.
With this route, 5km, you'll up and down in an hour. Linkback: https://mountainviews.ie/summit/384/comment/6679/

Straight forward out and back route on a Coilte track to the masts at the top. Make sure to take the track to the left at W13586 53096 C as this is the one that leads to the summit but if you weren't aware it does look like continuing straight on is the way as the correct track had a felled tree. Linkback: https://mountainviews.ie/summit/384/comment/20177/

Photo of summit taken from track up to hill Linkback: https://mountainviews.ie/summit/384/comment/1854/