The MACHINE variable allows to automatically set up some environment variables and job submission instructions for know machines. The are a few known machines already included: classical Linux and some super-computers. But you can add your own MACHINE set up by adding a directory in SCRIPTS_TOOLBOX/MACHINE.
Check the existing machines, and create a similar directory for your own machine with the same scripts inside (e.g. header.Linux, launch_Linux.sh, myenv.Linux, myenv.Linux.wrf, myenv.Linux.ww3, with Linux changed to your machine name). You obviously need to adapt these scripts to your machine.