just take on c6 then the c4 pawn and run the c pawn down...
Pawn ending
37. g5 & hxg5 - ouch. The h-pawn run plan outlined by tonydal looks like a winner for sure.
I think 42. a4 throws away the win and 42. Kxc6 is still winning for white. 44. Kxc6 seems to be the losing move but 44. Kc4 should draw with correct play from black (he can still lose if he messes it up).
That looked like a painful loss. I'm sure you will remember the lesson on pawn endings that this game is sure to have taught you!
The way to look at this position is to count the moves. You are at most 7 moves (5 for the pawn and 2 for the king to reach the controlling square of g7) from queening, and there is nothing else on the rest of the board the opponent can do in 7 moves to get close to queening. So 36. h4 is the mistake: you can't let his king cut you off from the controlling square at g7. After 36. Kg6 as maestro tonydal says, Black cannot cut your king off from the control square by Kf8, as 37. Kxf6 gives you 2 passed pawns to march in and also gives you the inside track to move your over and take as many queenside pawns as you like. So he has to play something besides 36. ... Kf8, and then you occupy g7 with the king and march the rook pawn in. If he tries 36. ... Ke6 to try an end-run-around, then you just march the pawn right away. Your king doesn't actually need to occupy g7 unless he actually threatens to cut you off from it. I hope this makes everything clear.
White[EDIT Black} to move. I lost this pawn ending as White.
I'm sure I could have done better?