To disable Secure Boot in a Xiaomi laptop, follow these steps:

1. Restart your laptop.
2. Immediately press the F2 key repeatedly to enter the BIOS Setup.
3. Use the arrow keys to navigate to the Security tab.
4. Press Enter to select Secure Boot mode.
5. Use the arrow keys to select Disabled.
6. Press Enter to disable Secure Boot.
7. Press F10 to save your changes and exit the BIOS Setup.

Your laptop will restart and Secure Boot will be disabled.

Note: If you are unable to disable Secure Boot using the steps above, you may need to reset your BIOS password. To do this, follow these steps:

1. Enter the BIOS Setup by pressing F2 during boot.
2. Navigate to the Security tab.
3. Press Enter to select Set Supervisor Password.
4. Enter a new BIOS password and press Enter.
5. Re-enter the new password and press Enter.
6. Press F10 to save your changes and exit the BIOS Setup.

Once you have reset your BIOS password, you should be able to disable Secure Boot using the steps above.