If it has head bolts , the same as any engine
if it doesn't , the cylinder will unbolt at the crankcase
undo those bolts and carefully pull the cylinder off the piston
mark the location of the cylinder so that assembly puts the exhaust and inlet ports in the right places
NOTE-- 2 stroke rings are pegged in the ring groove so when assembling the cylinder back onto the piston , ensure that the ring gaps are at the small peg or you will break the rings when pushing the cylinder down over the piston