game saves are stored in the app data folder, go to the searchbar in Windows, type %appdata% and find the folder called renpy, all your saves should be in the 'Ripples' folder. Just delete them.
Alternatively, a much simpler solution would be to go into Ripples, and in the save screen hover the picture of the save you want deleted and hit 'Delete' on your keyboard. That should work, and it doesn't require folder juggling.