Adding a new line into the trixbox

Hi

I'm new to trixbox, I have a TDM400P in the server and it's all working fine for both incoming and outgoing calls but they are all coming in on one of the four ports available for the TDM400P.

What I want to do next is add another incoming telephone line on a different port and have it go to a particular extension or group. How can I achieve this?

Thanks

manx1