Modeling, how to?

well, i have GCFscape, Gimp, Blender, but i think i need something to compress models or something. I think i have most of the tools needed, but how do I do it. I went to “Modeling, where to start”, but it was mostly a war over which program was better. I dont want to change programs, so im using what i have, but i’ll get any new ones i need.

Lets say i just wanna make a cube. I can go to blender, and make one, but, how do i get it to the game?

Well, I made my untextured model, but I’m stuck now.