Increase the number of Mags

OK, am very new to modding, this is for Sandstorm

  1. How do I increase the number mags, eg for MG3, heavy carrier shows 3 but in PIE only 1 shows.
  2. where can I learn to “rig” 3D animations, for guns, using Blender, I have downloaded an fbx file, where do I go from there?
    Please be “gentle” and nearly 67 and this modding thing is very alien.
    Thanks for any help