User script Path

[Anonymous]

Hi 
How do I do to add a USER SCRIPT directory, editing maya.env file
I've read the help but not understood at all and no want to make an "irreversible" mistake.
Just want to add this folder: MEL_NS
C:\Users\guinz\OneDrive\Bureau\Documents\maya\2019\scripts\MEL_NS

So that when I use the rehash command, the function reads the folder named above

rehash;