If you arrive via the bus, get off in town and catch a local shuttle or taxi to the trailhead. Don't plan on arranging horses upon arriving. Do it ahead of time. See the horses info page.
You can also opt to get off at the Cochamó-River bridge and walk or hitch the gravel road heading up river valley for 8 kilometers (1.5-hour-plus walk) to the trailhead, though, it's recommended to save your energy for the hike in and take a Cochamó-trailhead shuttle.
During the high season, there is a constant flow of shuttles running the 10 kilometers from the Cochamó town to the Cochamó Valley trailhead.