[Typo3] templavoila sub template

[Christoph Koehler]

Hello,

sorry for this really obvious question, but the FTB doc is kinda old, and  
I am not too smart. Maybe one of you guys can point me in the right  
direction:
I would like to have some pages of my site have a different template. What  
do I do? Add a new TO, or a DS, or both, and how do I do this? I played  
around with it and got the template to show on the sites that I wanted,  
but I didn't find any place to edit the TypoScript for that template to  
add a submenu or content or anything.

Thanks!

Christoph