Oh, then you won't be able to do most of the things you can with a website anyway. Thats why they're free. You can generally only do what it says in the Site Builder or whatever Tripod has.
If you can insert your own HTML into the site, then use Frontpage, make the website, (if you have Frontpage 2003 don't use Layers), and when its finished go to the Code Tab and copy the code and paste into the Tripod thing.