How to Download and Install OxygenOS 12 update on OnePlus phone

Here you have step by step guide:

1. Download the official Rom
2. Once the file is downloaded, go to the File Manager.
3. Long press the file to select it.
4. Hit the action overflow menu (three vertical dots).
5. Select Cut.
6. Hit Internal storage.
7. Hit the Paste button to paste the file in the root directory of your phone. Now that the file is in the requisite directory, you can go ahead with the local upgrade.
8. Navigate to Settings.
9. Scroll to the bottom of the page.
10. Select System.
11. Hit System updates.
12. Hit Install Now to manually install OxygenOS 12 on your OnePlus phone.
13. Once the installation is finished, navigate to the About phone page to verify the build number.

Yes, it’s that simple my friends.