Talk to him. Look at his animals. Choose the correct food to replace your twins' head (choose the food of the racoon, the squash). Put it on your twins' shoulder. Now go up and play the ballgame. Yes, you win! Now go back to the spinning wheel. Push any button 10 times to go back to the future.
Go find snakeskirt. Challenge him in the ballgame. Deflect his shoot 15 times and you'll beat him. Watch the scene. Then put the skull on the altar. Use the necklace with Xochi's necklace. Watch the ending scene. Kiss her now man!