That thing comes with all the kits and is the doohickey you use when you pull the gear for removing the clutch. There's a thread on this forum for using it and, by golly, I can't remember where it is.......someone help me out.
Welcome to the forum... If you squeeze the clutch lever, the rear wheel should spin freely. If not, the chain might be touching the crankcase or you need to adjust your clutch cable or the clutch itself...