How to update oppo system os via sd card

 First Download the firmware to the root directory of your SD Card
(A root directory is a top-most directory in the SD Card file systems).

1.Turn off your phone
2.Press Hold Power button with Volume Down button Together then
 (Choose Install from storage device) and confirm by Press Power Button

3.Choose From SD Card by Pressing Volume Down Button then confirm by Press Power Button

4.Phone will show directory root folder then find where your put the file update

5.Select your file update then Install by Agree confirmation. That's it ! Good Luck