You haven’t provided your Magento authentication keys

I’m new in using Magento. Ok, I use Mage-OS.
All is very difficult and sometimes no way to found a valide answer for questions.
So I’m happy to find these forum and hope of your help.

I want to install the german-language-pack https://commercemarketplace.adobe.com/wilma-digital-magento2-informal-de-de.html but don’t know about the verification.
I bought it. Yes, it’s for free.

When I try to install it, I get this message and can’t find anything about how to solve the problem. What username and password do I need to set?
enter image description here

Many Thanks, in advance.