Check the step-by-step user guide to learn how to use AceThinker Mobile mirror: https://www.acethinker.com/mobile-mirror/how-to-use-acethinker-mirror.html
As we know, Android comes in various versions. Therefore, enabling USB debugging may vary depending on your phone's Andriod version. As for how to turn on USB debugging, please turn to: https://www.acethinker.com/support/usb-debugging.html to find more details.
Are you having trouble connecting your Android phone to the Mobile Mirror via USB? You can follow this article to find some troubleshooting techniques you should do: https://www.acethinker.com/mobile-mirror/android-cannot-connect.html
You can follow this guide to adjust the display quality of AceThinker Screen Mirror on your Android and iOS device: https://www.acethinker.com/mobile-mirror/adjust-display-quality.html