Your router is a NAT router, as you were saying you wanna just open the port you need to connect to. So first you need to find out what ports UDP and TCP you need open, then open your Internet Explorer and type in the IP you've assigned the router. No need for any http:// etc.
From here, put in your password. If you haven't changed it, I'll assume it's admin / private . Next, go to Configuration -> Advanced -> Virtual Server. From here, create new ID's for both your UDP and TCP pinhole. Hey presto. Hope that helps