Open the PoS-App. You can do this in the Business Apps under Point of Sale or click Open in the tile under Point of Sale.
From there, select the Connect tab.
Now check under Connect wether the application QR is activated.
Click on Add.
Now, click on Install at QR.
Please click on Done - the QR-Code shown is not the QR-Code you need for use at the PoS.
Now, click on Close at the top right corner.
Check if the QR-App is still active, i.e. if the toggle switch is blue. If the toggle switch is still grey, click it to activate the QR application.
How to download / print the QR-Code and use it for PoS you can find out here.