*SPOILER WARNING!* The super secret password *SPOILER WARNING!*

[mikael]

I can't open the .rar file. Whenever I choose it, it asks me which program I should open it with.

Do you have WinRAR installed on your computer?
If you have it, just choose it as the default program and it will open.

If you don't have it, go here and download it, install it and then run the .rar file again.

… or if you are on a Mac, try The Unarchiver.