Isn't there tutorials that come with the FPSC entity maker? I got those and they helped a lot. But, are you saying you're having problems making the weapons, editing them, or exporting?
Wait, I think I know. Put the weapon you want to edit first at the top of the list of entities that came with the entity editor. Watch the tutorials for more help. Tutorial 1 is the best for helping you to get started (that's why it's first). That's the best help I can give.
Nothing is too hard as long as you can achieve it (*Note* This does not apply to programmers).