Steps to use the extended screen function

1. Make sure that your Android phone and portable monitor both support USB connection or connect through HDMI interface.

2. On your iPhone or iPad or Android phone, open the settings menu and find the "Display" or similar option.

3. In Display Settings, look for "Multiple Screens", "Cast Screen", or similar options, and enable that feature.

4. Select the appropriate display mode, such as secondary screen mode (as an extended display) or mirror mode (same content as the main screen).