If you look under the chaincase, you will see a plug. With a pan in place, remove the plug and the fluid will drain out. I like to remove the chaincase cover and check the chain and sprockets after it's drained. That also gives me a chance to adjust the chain tension. Re-attach the chaincase cover and refill with chaincase fluid (Polaris sells synthetic fluid that works great). It should take 8-9 oz. If you can't find Polaris chaincase fluid, I think Amsoil also sells chaincase fluid. In a pinch, you could use ATF.