Here we take the Xiaomi 8 mobile phone as an example. The steps to record the screen and sound of the mobile phone are as follows:

1. Open the "System Tools" folder on the MIUI system desktop, find and click " "Screen Recording" APP icon.

2. After entering the screen recording APP, click the "Settings" button in the upper left corner of the page to enter the screen recording application settings page.

3. In the settings application page that opens, find the "Sound Source" setting item and click to enter the setting options.

4. Next, select the "System Recording" option in the menu that pops up at the bottom of the page.

5. After the settings are completed, return to the APP main page and click the "Screen Recording" function button in the lower right corner of the page.

6. Next, you can see the screen recording tool button on the desktop. Click this button to start recording the screen. It will also record the sounds emitted within the system.

7. During the screen recording process, you can see the current recording time. After completing the recording, directly click the screen recording gadget icon to end the current recording operation and save it automatically.

8. Finally, you can see the recorded video on the main page of the APP. Click to play the video animation and the internal sound of the system.

Screen recording can be found directly in the drop-down menu. Most Android phones can find the screen recording function in the drop-down menu. If not, you can add it yourself in the drop-down menu. Open your phone, find Screen Recording in the drop-down menu, turn on the option to record ambient sounds, and then start recording.