It sounds from your post that you want to use the bittorrent GUI front-end. I don't know what file manager you use, but you need to set the file association for *.torrent so that when you double-click on a *.torrent file, you execute the command: btdownloadgui --max-upload 12
(It's a good idea to limit your upload rate so that you don't choke your bandwidth pipe).
I personally stay away from the bittorrent gui programs like
Azureus, and stick to the commandline versions. If you are feeling adventurous, open a terminal program (like xterm or konsole, etc) and at the prompt, do:
prompt$ cd /path/to/your/torrents
prompt$ btdownloadcurses --max_upload_rate 12 filename.torrent
If you want to launch many torrents at once, then do:
prompt$ btlaunchmanycurses *.torrent --max_upload_rate 12
(on your system, btdownloadcurses may be btdownloadcurses.py, and btlaunchmanycurses may be btlaunchmanycurses.py)