I get it from github, https://github.com/TeraTech/MMM-WiFiPassword, and I follow the installation guide.
"Installation
In your terminal, change to your Magic Mirror module directory
cd ~/MagicMirror/modules
Clone this repository git clone git@github.com:TeraTech/MMM-WiFiPassword.git OR git clone https://github.com/TeraTech/MMM-WiFiPassword.git"
Then, in terminal, I should enter username an password. I tried my github isername and password, but I think my account is not, what is recommend.
Jochen