Parking is available at Kreuzeck (Cable-Car) or at the Aule-Alm. Follow the signs to "Rießersee". Soon you will find signs to the track. You will reach the old Bob-Shed and the old elevator.
From the Station "Garmisch-Partenkichen" you can reach Rießersee and the bobsleigh track in about one hour. But you also can take the Zugspitz-Bahn to Kreuzeck station. From there you have to walk about half an hour to the Bob-Shed.