There may be some issues with the webpage, the download process should be really simple. You hit the "Download now" button, then to get the game for free, you hit "No thanks, just take me to the downloads", there you hit "Download" next to the newest version. The game has no setup, as soon as it downloads, you can extract the .zip file and open the executable.
If you still have trouble, maybe try to download the game at some other time, OR maybe try another browser, I'm not sure what your issue might really be, as the downloading process is really outside my reach