how do i mod this game? Thread

ive been playing a game that i really like but ive wanted to change the sprites to add a bit more spice, yet theres no tutorials that i can find, all i can find in the files of the game is just save files, some music and the icon but thats it, anyone know how?
The game is cat goes fishing and was made in gamemaker studio

All files(pictures) are in that file called data.win, just tested, but before using some specialized unpackers you have to have permission from game developer.