How do i change my default bittourent client?

-right now, when i download something from pirate bay, frostwire (similar to limewire) downloads it. how can i change it so that when i download the torrent, transmission, my new client, downloads it automatically. thanks! sorry for my crappy computer lingostart menu> predef programs> define associations> look for .torrent

i don't think those are the real names in english, i'm portuguese.

good luck