The problem is that I have no idea how you got that model in the first place. I need somebody to explain how to make my model from scratch and eventually texture it and such. (In XSI)

I don't know anyone here did model work from scratch in XSI. It really doesn't matter what program you use so long as you can save it in a format you can import into XSI (usually .obj). Just google XSI modeling tutorials or videos if you don't want to use anything else, when making the base mesh it doesn't really matter what its for (though try to keep it as one mesh object).

I will say that texturing in XSI is not fun, and you need to make the texture first then hand map every polygon in the UV map to the proper spot on the texture sheet. I imagine their must be better programs to do that with.

me   All the models created by me were done in XSI. I learned XSI first because I knew it was crucial to getting models into Sins and frankly just don't want to learn anything else at this point.

I'm not recommending it as a the best modeling tool, just saying

Can be tough but it's possible. I textured the entire Hypercorp race using XSI with two texture sheets: one for ships and one for structures.

http://www.moddb.com/mods/sins-of-the-fallen/features/hypercorp-race

There are other tools. I also use a 3d paint program and know of atleast a couple others that use something similar.

There's also several free tools that I know Thoumsin has written about if you like data mining (not going to do it).

Didnt know you were into Space Battleship Yamato