Starting point: Eau Noire car park in Waimes.
Please note that if you type "Eau Noire car park" into Google Maps, the app may take you to the Sourbrodt container park, which is approximately 500 metres from the Eau Noire car park, because it considers the last 500 metres to the car park to be impassable, which is not the case.
There is a sign indicating the route of the Balade des gens heureux at the entrance to the car park. Then simply follow the "Ballade des gens heureux" arrows or follow the route on the Visorando app, which is why I don't think it's necessary to describe the route.