You have to click the beating heart and get Hearts by that when you have 100 Hearts you can by the Heart pass there you can unlock skins but they will also cost some Hearts when you have the Heart pass it says how much a skin costs under the name of the skin.
Thanks to @Melloganggames 2 more skins are coming I can´t say exactly when they are gonna come but hopefully it will take less time than the other 2 skins:) --------Just to remind you the game is incomplete--------Hope you like the game!:)
