The warming hut is not accessible by car.  There's a flat trail leading to it from the Shafer Run parking lot - see the trail map.  To get to Shafer Run, take Rt 31 to Bakersville.  Do not attempt to use Tunnel Rd to get to Shafer Run in winter!  

There are also 2 parking lots on Tunnel Rd.  Note that reaching any of these parking lots often requires 4WD.

North Woods trail map

Laurel Highlands Nordic Ski Patrol patrols this area at weekends.

Winter recreation guide from Forbes State Forest
Forbes State Forest trail map
Forbes State Forest map collection