Create your side. Look here to get that part done: http://swbf-custom.forumactif.com/t141-faqicemember-s-tutorials-in-to-modding
Create your weapon odf file. I named mine
Place them in my sides odf folder. You place your weapon files in your sides odf folder.
Open up the odf file and place the name of your weapon model in the locations with red arrows.
Save your weapon odf file.
NOTE: Make sure your weapon model is in your sides msh folder with your weapon skin.
Now open your soldiers default odf file. Mine is named: r39_inf_default_rifleman
Place the name of your weapons odf file shown in the picture.
Munge your side and see your weapon ingame