Head off the doubletrack which soon turns into singletrack as you make a short climb. You'll head through a pass then descend some narrow parts, before hitting a steep, sketchy switchback. Below this, the trail follows an old road and while loose, is flowing and fun.
Eventually, you'll come out onto Black Canyon Road. For Poleta Canyon, make a right, then an immediate left to start your climb. Don't attempt to climb straight up Black Canyon Road, as it has been blocked off to keep motorcycles out, and will not be fun.