TMPGEnc 4.0 XPress - 16:9 to 4:3 (or How to use both sizes with DVD-Lab Pro 2.3)

I'm using TMPGEnc 4.0 XPress, version 4.2.3.193 to edit avi and wmv
files and make them DVD ready for authoring.

When the source is 16:9, I'm pretty sure I've been able to get the
output to be 4:3 by changing a setting. Now that I want to do that
again, I can't seem to find it or remember how I did it.

Can you help?

An alternative would be to learn how to use both sizes on a DVD using
DVD-lab Pro 2.3 Is there a tutorial somewhere on that?

Thanks.