From Saint-Pée-sur-Nivelle, take the old road to Saint-Jean-de-Luz (D307).
Shortly after leaving Helbarron, at a place called Marmantzua, there is a wide track on the right where you can park.
(S/E) Continue along this track northwards until you enter a wooded area and come to a T-junction.
(1) Turn right onto the path that runs along the edge of the forest and leads to a wide track.
(2) Turn left, still along the edge of the forest. Continue until you reach a crossroads forming a triangle of paths.
(3) Turn left again, heading south-west, to descend to the crossroads you encountered on the way up.
(1) Follow the same route back to the car park (S/E).