Great, Rob, thank you very much! I found it.
This is well hidden indeed, and I could not find any documentation on or link to that download on the Wolfram website.
Actually it looks a bit different: Directly on "My Account" there is a box named "Wolfram Programming Lab - Standard" with some information about my licence. The box contains an entry "Desktop Product: Windows|Mac|Linux". Clicking on "Windows" starts the download.
I will start the Installation after the download has finished and let you know if it worked.