making and skinning a gun

[aazumak]

plz people i need help. ive been making this gun to replace the bar for bout a week and i cant seem to texture it. (im also wondering what a bone is and how to create one, because it wont let me export without a bone)

im using milkshape and im in the texture editor thing, but no matter what i do i cant get one part to go on something. ive selected the part that says bottom (while in the bottom side of the object is selected in box)

what am i doing wrong?

but when it doesnt goto the bottom side of my image!!!!1 plz help me