Real simple. Once the old headpipe(s) are off, simply pull the metal gasket out with a screwdriver or pick. The gaskets will come out in one piece and then slide your new gaskets into place.
Getting the old ones out is pretty easy...putting in the new ones can sometimes be a PITA. I've had to use a few 4-letter words & take breaks to cool off - they're tight.
Yeah, they can be a b!tch but I've found that a slight bit of oil on your finger swabbed around the exhaust opening makes for a fairly manageable insert. Works quite well.