If you are having a walk near Byrness and have just hiked Byrness Hill and Houx Hill, then the next one on your path will be Ravens Knowe.
From the parking, cross the road and find the fingerpost leading you up onto Byrness Hil, then follow this all the way to Ravens Knowe. There is a little cairn marking the summit.
Follow the route above or find it on OS Maps. It's around 4.5km and 346m of ascent.