Loosen the 4 allen head bolds on the back of the swing arm, put an 8mm allen wrench or anything else that will fit (screwdriver) through the back sproket into one of the holes on the swingarm (You will see them when you look down there). and then push your bike forward until the allen wrench or screwdriver hits the sproket spoke and that will tighten it. Roll backwards until the allen hits the other sprocket spoke and that will loosen it. I usually have to go back and forth a few times since having paddles on makes it roll un-smooth (did I just make up a word?) Once you get itwhere you want it tighten the allens on the back of the swing arm and you are done.
Don't go too tight!!!! The chain needs to have a certain amount of slack - this should be listed in the manual. Do NOT tighten it to "look" tight. It should have an inch or so or play.... or else you buy a new one! :thumbsup: