You'll see him in chapter 1 by where you get Gong. Talk to him. He won't join you right away. In chapter 4 in Pao town 1 (before the caravan moves), go to the priest's hut in the northwest area of town. Walk along the west wall INSIDE the hut. You should see Jogurt in the top left of the screen trying to flap his arms to fly. When he stops flapping, he'll be on your team.