Router wont let me play online!

I've tried to play online with some of my games, mainly Left 4 Dead, and it seems that a lot of people have had the same problems as me. apparently the problem is with the router. Mine is on here -

http://www.smc.com/index.cfm?event=viewProduct&localeCode=EN_USA&cid=1&scid=17&pid=924

i can use browsers and everything but whenever i try and connect to play online, theres always something wrong. I heard that by changing your routers IP address or something you can fix the problem, but I'm not that tech savvy. Ive researched this thoroughly on the web but its really complicated from what I've seen. I need some sort of simple explanation of how to fix this..

 

can you be more specific? how do you enter the settings?

 

Usually typing 192.168.1.1 or 192.168.0.1 into your internet browsers address bar will give acces to these settings.
The router will ask for a username and password which can usually be found on a sticker on the router.
I would explain in more detail but i have to go out.