Enable Developer Options on your phone, turn on USB Debugging and OEM Unlocking, and connect your phone to a PC. Use ADB and Fastboot commands on your computer to unlock the bootloader and flash the TWRP recovery image. Step 2: Download the Files
The of your Oppo A9 (e.g., A9 2020, A9 2016)? Which Android version you are currently running? Oppo A9 Custom Rom