Type your IP address into your browser and a login thing should pop up, unless you've changed the name and password, the login should be "admin" and password should be "password".

Just go to 'advanced settings' and go to 'port forwarding'. You should be able to input some ports there to open them up.

If you have a firewall on, also make sure you open up these same ports.

Sorry if that's vague, but I can't be bothered.