Unfortunately, the installation instruction at http://guillep.github.io/DBXTalk/garage/installation.html seems to be buggy. At least it did not work for me.
Therefore I wrote this step by step description how I finally had success. It is for those wanting to use Pharo7 on Microsoft Windows 10 : Accessing_MySQL_from_Pharo7_Smalltalk.pdf
I hope this text is as helpful for others as it would have been for me, if I had found something similar three weeks ago. ;-)