To setup Google Single Sign on login to your Backup Radar account first decide whether you want to lock down your logins to only Google Sign on accounts. To lock it down to a specific domain you can turn on Google enforcement for login and setup the domain(s) you plan to allow.
If you have an existing Backup Radar account you can login to that account and then click on profile at the top right of the menu:
Then click to turn on Google Account as shown below:
Once you do this you will be prompted to login with your google Account:
You should then see a confirmation it has been linked: