Creating a do I do this?

I've been playing with this nifty little program for a few days. I've been able to create a few tracks and even play them in rFactor no problem. I love how simple the program is to use, but I am completely unsure on how to create a pit-lane with tarmac for the tracks.

Do you first create a circuit and then add an "open track" to it for the pits? Currently, I've got cars running over "terrain" as the pits, but I'd like to have them running over tarmac instead.

How can I learn what I need to do to create a full circuit with a tarmac pit-lane? Will I need to "merge" two tracks together to achieve this...? Help please and thanks.