You simply have to be able to telnet (or ssh) into your router. And chances are that you have done it already if you are installing Oleg's firmware.
Code:
ipkg install enhanced-ctorrent
then you can cd to the directory where you have stored the torrent file and
Code:
enhanced-ctorrent -s filename.extn -i your.ip.add.ress -e 12 -p 6881 eg.torrent
Which means that file will be saved to your_new_filename.extn torrent will listen to your.ip. interface at the port 6881
requirements for this obviously is to have set up your HDD and screen also would be a good idea. See Marcnesium's tutorial in 500gP tutorials section