If you attempt to turn the speed dial on your scope and it will not turn, the speed ring on your scope is locked.  To unlock, slide the ring forward on the scope.  When you see that the ring has moved approximately 1/8-inch forward, the ring should be free for you to turn clockwise or counterclockwise to adjust the speed.  Turn the dial so that the triangle indicator on the scope is pointing to the speed of the arrow you are shooting.  To lock the ring, simply slide it backwards approximately 1/8-inch. 

NOTE:  Not all TenPoint variable-speed scopes have locking speed rings.