Visit this link:
https://providers.cloudsoftphone.com/qrgenerator/index
You will see some fields to enter the user's information
Cloud Id: Enter the domain
Username: Enter the extension
Password: Enter the password
Click Generate
This will download a jpeg of the QR code, you can then share this with the user:
They must open the mobile app, and tap on the Scan QR button
The camera app will open (you may need to allow permissions to use the camera) and if the user points it at the generated QR code it will auto-fill the username (ext@domain) and password and automatically log in the user.
Once logged in they should see their username in green in the top corner.