first of all, the chances are the tape will have contaminants on it such as lubrication from the deck mech. clean it with pure alcohol from the chemists' and a clean cloth.
looking at the cassette from above with the shutter facing away from you, on the RH side there's a little lever ; pull it towards you and lift up the flap. prop it open by inserting a little piece of folded cardboard or similar into the gap between it and the cassette to stop the tape being more creased.
next you will need two small flat bladed screw drivers. Turn the casette upside down keeping the flap facing away from you. Between the 2 spools towards the cassette spine - nearest you -you'll see a recess, poke one driver gently into the hole and slide it towards the spine; this releases the spool lock.
Then, using the other driver wind the tape into the shell by inserting it into the right hand toothed spool hub and turning the spool clockwise.
bear in mind that when tape is damaged it may shed particles into the tape path of the playback machine, temporarly clogging the head and giving a blank screen. this can sometimes be overcome by playing a fresh tape for half an hour or so to work the dirt out. If the tape is really wrinkled this may damage the heads.
I'd suggest copying it to a new tape or a pc, and when the picture starts to break up where the damage begins, stop the tape, eject it, manually wind it past the damaged section (see above -release spool lock and turn hub) and play it again to get the end of the recordings.
good luck!
Oh yeah, take the camera to a technician for expert attention before using it again.-