To enter the Seven Coloured Earths of Chamarel you'll have to pay a fee at the entrance gate near the beginning of the road based on the number of occupants in your vehicle. Various hotels also offer shuttles here. Parking is at the end of the road making it easy to find.
This trail starts at the parking area, passes the guard booth, and then heads towards the dunes. Once at the dunes the trail passes around the eastern edge of them. You'll pass a gift shop and display of the Seven Colors, a short route to a display of the endemic giant tortoises, and then come around to the "far" viewpoint.
The trail is very easy, and accessible to nearly everyone. Views from the east over the dunes are possibly the best thanks to a mountain backdrop.