You havent suggested what site you are wanting to forward one of your routers ports too, most people make this request for torrent download and/or gaming experience/improvement. Either way you need to know what port the software you are wanting to open a port for is currently using so you can tell your router which port to allow unchecked access.
I use this very informative support website for port resource info, click this link and choose your router type, in your case select Speedstream-5450
which will be the same setup as the 5830
That should take you to this page
Then select the software you are wanting to open the port for.IE: Utorrent or world of warcraft Etc... That will then open a detailed walkthrough on setting up rules for your routers port activity. You will need to follow the guide for each port you open, if the guide is not listed for the exact software you are using just read through the one supplied for Utorrent and change the port numbers to the ones you are using.
The software you are using should show you what port is in use at the time you are using it, some software may use a different port everytime you open the software or allow you to allocate a port permanently (which is not recommended safe internet practice especially if your ISP supplies your connection via a STATIC IP address, most use a DHCP allocated IP address)
Failing that you can find the port currently in use information using the command prompt- for winXP and Vista type c:/netstat-b for win2000 type c:/netstat-p Look for the software you are using it will be on the left hand side and look something like [Utorrent.exe] follow the line of info too the right and look for the 4-5 digit port number.
Wheeeew, Good Luck :0)