If you have d-link:
Open up internet browser, type this in address:
192.168.0.1
Username "Admin"
Password leave blank. Look around for port forwarding options (research before hand to know which ports for TCP and which ports for UDP you need to "
pen" (allow through).
For Linksys:
Open internet browser, type this in address
192.168.1.1
Username "admin"
Password leave blank
Same deal, research ports before hand, look for the option, put 'em in.
Good luck!