Place it in the root folder (Where you see the game exe, the game folder and the renpy folder), once that's done, just select the file and run it, (the enter key will do).
Once it runs, hit enter once and you should see a list of options, hit 1 and enter, then hit n when it asks for a prompt and then hit enter and just let it run for a minute or two and it'll extract the rpa files.
From that point you can just view the images.
(Tip: To speed up the extraction when you only want the images, cut and paste all rpa's except things like Images.rpa and Archive.rpa if applicable and just paste them to the game root folder while you extract then move them back. Saves unpacking the scripts etc.).