go in your browser, go to 192.168.1.1 and click on advanced tab. Then click on the fowarding tab, forward the port 6346 to your lan address (i.e. 192.168.1.100.)
then go to http://192.168.1.1/Status.htm to copy your ip address

go in limewire in preferences - advanced- firewall
click force ip and then enter your ip address.

you should start having uploads. if you have a dynamic address by your isp, you will have to change manually your ip in limewire every time you change ip in http://192.168.1.1/Status.htm, if a web site is served by your computer, you can enter the web site address in the limewire's firewall preferences.

for further informations search on google