You first need a BitTorrent Client to download PS-0.19. The page you found is actually the official BitTorrent client, but I think you can get an easier software that will donwload the stuff anyway.
1) First get
uTorrent (this is the name of the software), it's already the exe, so just put it where you like and run it.
2) Get the .torrent file from the download page which contains the information about the data you are downloading (PS-0.19). You can also get it from here:
torrent. Save this file somewhere you can find it easily.
3) Star uTorrent, menu File -> Add torrent -> Select the file downloaded (point 2). Select where to save the files and wait for it to complete.
Note: the program, at the first start, may ask your connection information to maximize speed.
I hope this can help.
Regards, Xayton