To be clear - THIS IS THE RIGHT WAY (see picture)
Its tested and worked fine for me. Make absolutely sure that you have closed TruckerMP (Launcher) and Euro Truck Simulator 2.
Otherwise restart your computer, verify that all files are in the correct directory.
For example my directory looks like this: C:\Users\Kaan\Documents\ETS2MP\mod
You should have a similar directory (besides the Username, huh).