Hi. Sorry about that. I have updated the download&install instructions now.
Basically, if you want to play it on your PC/Mac we recommend using an emulator called VICE. Remember to use the latest version of Vice to get the best emulation.
You can download VICE from http://vice-emu.sourceforge.net/
When you have started VICE, you should be able to drag the d64-file to VICE and it will run the game.
Let me know if you have any more issues! :-)