From Evanton there are a few ways up.
Start at the path up to Novar Quarry at the back of Culcairn (NH606666)and keep going northwest. At the junction after you go under the pylons (NH599680) bear left and as you go west along the forest road, just about any right turn will take you up to the track along the top of the hill.
Popular turns include NH595677 (very steep) NH582670 (less steep) NH569682 (less steep again but longer).
Once on the path along the northern side of the woods make your way along north east (ish) to Fryrish.
Coming down is faster via NH596695 to NH601690 (uphill to) NH596685 NH595684 NH600682 and then back the way you came.
Be careful of the "Novar 2" windfarm building which is going on at the moment and has turned many of the forest tracks into motorways.