As there are a number of small steep roads to the north it is best to follow a route, marked in blue on the Google map above if you enlarge it, from the junction near the Texaco (Beran) Filling station (LL55 3NF) 

Views of Tal y waen are shown on Google streetview below, The Barn Ysgubor is hidden behind the trees to the right but can be viewed by moving along the road to the right  and then panning left.