The Browns Creek Trail starts just down the road from the Browns Creek Trailhead, according to the map.
The lower portion (1.2 miles) of the Browns Creek trail is horribly washed out and extremely rocky, filled with massive baby heads. I would advise against trying to ride up it, although it's rideable (except for one hike-a-bike portion) on the way down.
The rest of the trail continues another 4.6 miles up into the mountains, past Browns Lake, and then it connects to a 4x4 road. Using the 4x4 road the Browns Creek trail can be looped with the nearby Little Browns Creek Trail.