For maximum performance when using BitTorrent behind NAT, you should open ports 6881-6889 to your PC. As of version 3.2 and later, BitTorrent uses 6881-6999 though you should be fine with the smaller range.
Of course, other programs use different port, or random ports or other well known ports. You will have to know what ports your client users.
To open these ports, create an Inbound NAT rule matching the following, changing 192.168.1.22 to the IP address of the system using BitTorrent.
If you aren't already using a static IP or static DHCP reservation, you should set one up for that machine now so its IP address will never change.