What if my phone is already set up so this screen isn’t available ?

For information on restoring to a phone that is already set up, see the following from: Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

1. Turn on your device. You should see a Hello screen. If you already set up your device, you need to erase all of its content before you can use these steps to restore from your backup.

As the article linked above states:

”If you already set up your device, you need to erase all of its content before you can use these steps to restore from your backup.”