If you were lucky enough to get your clutch cover gasket off in one piece and it’s still in good shape, you can technically reuse it. But gaskets are inexpensive, and it’s always a good idea to use a fresh one. Double check that the dowel pins are correctly placed, and then reinstall your clutch cover. After that, just reattached the clutch cable, add engine oil if you drained it, set your clutch-lever free play, and go ride! It’s a good idea to recheck your free play after 100 miles or so.