Unscrew the wire, shove the bale forward & remove the coil. Replace the gasket. Gently pull the pig tail & bend the tab to insure good contacts when you put the coil back on the distributor.
If the coil is loose when you re-install it, replace the bale or put a piece of cardboard under it.
But the bigger question.......
As coils rarely fail unless you left the key on, why are you replacing it?