There are 2 bolts on the rear end to loosen up. Usually alum bolts. Make sure they are good and loose. Looking at the rearend from the back to the right of the sprocket there is a big collar that slides through your rearend that the axle runs through just turn that collar one way or the other and your chain should loosen or tighten. There are usually holes in the collar to stick maybe a large punch or large screwdriver to turn it. Be sure not to get your chain to tight because it needs room to flex. Tighten up the two bolts back up good and your ready to go.