Here are the steps, most important is the first one.
1.
Setting up a Static ip for VISTA (this number will be used in step 2 so make a note of it)
2. Go to this page, look for Belkin at far left column, then find F5D5231-4 (#5 or 6 listed under Belkin)
PortForward.com - Free Help Setting up Your Router or Firewall once you find your model, click on that link, then find LimeWire listed on following page & click that. Directions are there.

Note: in the LW settings, both listening & connection ports are best kept the same.
BTW yours might be a variation of the F5D5231-4 so check which one looks most similar. eg: F5D5231-4v3