@ Jae
If you are behind a Linksys router, open up your internet browser and type 192.168.1.1. Type admin as the password. This will take you to the routers page. Click advanced, then forwarding. Set the ports you want to open, enable Protocol TCP, and check the enable box. Next all you need to do is hit apply.
The page you should be on should look like this.
Click the image to enlarge.: