After installing the 3CX application it will prompt you to scan a QR code.
To find your QR code, please go to
https://itservices-dmat.3cx.co.uk:5001/webclient/#/login and sign in with your ext. number and password (this should have been emailed to you.
After you have signed in, click on the profile picture in the top right hand side and click "scan QR code".
This will bring up a QR code for you to scan and sync your account with the application.