i want to put a web page on a different webpage...for example...i want to keep the navigation bar where it is, and the inside a forum or somthing....any know how to do this?

don't really understand wat u mean.

Frames - http://www.lissaexplains.com/frames.shtml

can you like put a webpage in a table?cause im useing a page builder and you cant make the navigation different thing...if you know what i mean...

not with only changing one part.
Ditch page builder and use notepad or something better. You'll be able to do it yourself, have better control and won't have all the jumbled code pagebuilders tend to add.