Download the bittorrent client. I use bittornado and you can get it here:
# tar xjvf BitTornado-xxx
The cd into the new directory and read the installer instructions. Probably just:
It requires python and wxpython for the gui. Then you can launch it doing:
Check the settings to make sure the ports the client is using is open on your router and or firewall and you should be good to go.