Environment variables at ~/.profile

export KIGITHUB='https://github.com/KiCAD'
export KISYS3DMOD='/usr/local/share/kicad/modules/packages3d'

Log out, log back in.
Enter this in terminal:

$ sudo ln -s /KiCadLib-master/3D /usr/local/share/kicad/modules/packages3d/3D
