You have to take the via ferrata equipment with you or you can rent it at the Imholz Sport Andermatt shop. This should cost about 20-30CHF. The starting point of the via ferrata is at the bottom of the gorge, if you follow the signs when walking to the bridge, you should see the entry. After that it goes steep to the top of the gorge. You will ascend several hundred metes before reaching the top.