When you say you want to "make it portable" do you mean so that you can play it on other computers, or on a DVD player?
In either case, first click Start?programs/Nero 7/Nero StartSmart
If you want to play it only on other computers, select Data from the top line, then Make a Data DVD from below. Drag the AVI file into the main window, then click Burn
If you want to play it on a DVD player, select Photo and Video from the top menu, then Make your own DVD-Video from below. Choose Add Video Files, select your AVI and open it. Click next, next,next,burn