hi there

basically there are two 3d design programs.
there's GMax, it comes free with Fs2002 pro and FS9,
and FSDS... which you have to purchase i think

i think most people use gmax around here, i do...
in the sticky thread on the top of the page, you'll find the FAQ... also there are a lot of tutorials here on how to do basically anything with both programs... they're a lot of help for begginers and advanced users. sure worth checking out

Hope this helped

C ya
Moach