How do download torrents with ApexDC++?

I am trying to download files from bt.etree.org. I downloaded the torrent and saved it, and I downloaded ApexDC++ as well. I don't know how to open the torrent file because the file type apparently is not supported on my computer. Could anybody give me clear instructions on how to download files from a website like this? Also, is there a better free program I could be using?