From the Bern area:
drive to Interlaken along the lake of Thun.

From the Luzern area:
drive to Interlaken over the Brünig pass.

1) Stay on the Autobahn A8 that goes around Interlaken. Do not enter the town

2) Exit the Autobahn at the "Wilderswil, Grindelwald, Lauterbrunnen" exit.

Follow the signposts to Wilderswil, Grindelwald, Lauterbrunnen – drive through the village of Wilderswil and continue straight on up the valley to Lauterbrunnen.

Drive through the village Lauterbrunnen and continue to Stechelberg

After about 6 km, enter the car park of the Schilthornbahn cable car on your right

3) Park your car and take the cable car up to Gimmelwald. (Parking costs)

Exit the cable car station and you will see the Mountain Hostel sign up to the left

Walk up the little path to the left across field to get to the mountain hostel.