When you have two passed pawns, this may help you win the game.
In case your opponent has a protected passed pawn, things may be difficult though.
White to play. Can you win this endgame?
When you are familiar with the "rule of the square", you might be able to solve this position.
In this position six things are important.
First: the white pawns can't promote without help of the white king.
Second: the white king can advance to f4 without leaving the square of the passed pawn c4.
Third: the black king has to guard the connected passed pawns. He has to stop them from advancing, so he is stuck on the kingside.
Fourth: the black king isn't able to capture the defending passed pawn, because the other passed pawn would then be unstoppable.
Fifth: the white king may step out of the square if he can help his pawns promote before the black pawn does.
Sixth, and this is the thing you have to know already (or to calculate for yourself during a real game): if the white pawn queens, the black king can be mated.
Armed with this knowledge, you'll be able to come up with a plan.
White has to get his king to the kingside, to help his pawns move forward: 1. Kd2.
And black has to keep his king in front of the white pawns, to keep them from promoting 1....Kg4.
White can now play 2.h4, starting to move the pawns forward.
The black king has to retreat. If black would play Kf5 now, this would allow white to play h5, moving his pawns forward again. To prevent this, black plays 2...Kh5.
White is going to bring his king further to the kingside now. 3. Ke2, Kg4; 4.Ke3, Kh5; 4. Kf4.
The white king is still in the square of the black pawn.
The black king has to retreat once again, giving white the chance to move his pawns once more . 4....Kh6; 5. g4,
5....Kg6; 6.h5+, Kh6;
White has the move now. He wants to create this position with black to move, as black to move would have to retreat once more.
So he starts a triangulation, to reach this goal.
Notice that the white king is free to move around, as long as he stays in the square of the black's protected passed pawn.
7. Ke4, Kg5; 8.Kf3, Kh6; 9.Kf4,
Now white has reached his goal an black has to retreat. 9.... Kh7; 10.g5, Kg7;
And this position is a crucial position. There's only one winning move here. 11.g6!,
Black defends with 11....Kf6 (or Kh6);
So White will have to perform one more triangulation to reach the g5-square. 12. Ke4, Kg7; 13.Ke3, Kf6; 14 Kf4,
Black has to give access to the g6-square now.
After 14....Kg7 (the usual defence, although Ke7 is tricky too) White has to leave the square of the black pawn to make progress, so 15. Kg5!.
When leaving the square in a real game, you'll want to be very sure such a move doesn't lose.
Now there's no way back. Black will queen his pawn, so White has to make sure he has a winning sequence. 15....c3; 16. h6+, Kg8; 17. Kf6, c2;
18. h6+, Kh8; 19. Kf7, c1Q;
The black pawn has promoted. However, as it didn't promote with a check, it isn't dangerous.
20.g7+, Kxh7; 21. g8Q+, Kh6; 22. Qg6#.
Here is the winning position. If the black king hadn't been checkmated, the position would only have been a draw.
If the c4 pawn were on a4 in the starting position, or if the passed pawns were on the f- and g-file, then the position is only drawn.
I hope you understand this endgame now.
My advice for you is to practice it (with a chess friend) several times, until you eventually know it by heart.