Follow these instructions precisely.
A new option in the Advanced menu to permanently install a temporarily booted recovery image. Installation Overview twrp-3.6.0-9-on7xelte.tar
Your device's bootloader must be unlocked (often requiring "OEM Unlocking" to be enabled in Developer Options). How to Install twrp-3.6.0-9-on7xelte.tar Description 1 Enable OEM Unlock Follow these instructions precisely