Drive or take the bus to Leysin. There take the Cable car to Berneuse (15CHF round-trip for an adult).
From Berneuse hike down towards Lac d'Ai, and then up again on the opposite side. It's easy, just follow the chairlift lines down and then up again.
When you reach the top of the hill, you'll see the Ferrata start on the right side. There's a big white sign which identifies the start of the tour.
Parking can be done near the cable car station. The price is 4CHF for 5h and 5CHF for 8h.
Alternatively, there is a free parking next to the sports center in Leysin. That will require an additional 15min walk to the cable car station.
This functionality is only avaliable for members of the outdooractive plattform.