just read and do exactly as described:
Please make sure that your phone has Android version 13 or 14
after unlock
7.14 Disconnect the USB cable from your phone. Then, turn the phone on and let it boot up to the UI.
No need to run the “Get started” phase (if requested). It is good to stop there. Just turn the
phone off. This will complete the unlocking session.
and then you can flash…