To use the Sign-In App Companion application on your phone, you'll first need to install the application from your relevant app store, below are the direct links for Android & iOS
After you have installed the relevant application to your device, you will need to raise a ticket or speak to a member of AIT so that you can be invited to use the Companion App, once you have been informed that an invite has been sent, you just need to open the application on your device and then enter the 12-digit authorisation code from the invitation email.