Installing on Ubuntu 18.04
a file named config.js.sample just rename that one to config.js and should be work.
What you are supposed to do is make a COPY of the config.js.sample (so that you never lose it) and rename the pasted copy to config.js.
Once you have MM running you can press Ctrl M to hide MM and use your PC for other things. Simply clicking the MM icon in the task bar will bring MM to the front.