It seems like you need to learn how to install programs on the Mac. When you download a program, it typically is a .dmg file. When you click on this, it will open a "disk image" file which will look like a little white disk drive. Open that, and you should see an icon for the program. Don't click on it. Instead, drag it to your "Applications" folder in Finder. That will install the program.
For torrents, I recommend Transmission. It's really light and quick.