Hello,
Windows user here. Using MCUXpresso's makefiles is all a matter of %PATH% variable.
I found that the easiest way to run "make" commands from the command line is to Ctrl-click on the project name in the bottom right-hand corner of the MCUXpresso IDE:

This will open a terminal window in your project directory with %PATH% properly set, so you can enter "make clean" and "make -j8 all" and similar commands.
Of course, you can close the IDE and the terminal window stays open. You can also inspect the %PATH% variable. Set this path in any other terminal window and you can run make commands there as well.
Hope you can put this to good use.
Best regards,
Daniel