For the most types of backup (beside VHD and SystemState), the only setting that needs to be done, is choosing a "Start backup as a Windows user" option on the Advanced settings tab and enter the system administrator credentials.
You can also edit the existing project and set this option.
When you need to create a VHD or SystemState backup, you need to go to system services - right-click on the tray panel and open the Task Manager. Then go to Services tab and click the Open Services button (the last option name can be different on various Windows versions).
In the new windows, find the Xopero_backupagent option. Right–click it and choose Properties.
In the properties window, go to Log On tab. There, you need to check This account option and enter login and password (twice – in both password and confirm password field) of Windows Administator.
After entering right credentials, you need to click Apply. The service have to be restarted now. To do it, go to General tab and click Stop and then Start. If the credentials are valid, the service will be started.
After configuring above settings, the backup service will be given needed admin rights to create a VHD and System State projects.