Go to 192.168.1.1. If your settings page looks like this, follow ahead.
Go to Advanced, Then 'NAT', then Virtual server and add ports from there.
Don't forget to set a static IP from Network settings as well, otherwise it's useless
I'm using 192.168.1.56 (You can put any number between 2 and 255 in place of 56), but you must use this IP when opening the ports.