You will need to flash a tool like TWRP (Team Win Recovery Project).
Because Oppo prioritized the "Selfie Expert" experience over long-term OS upgrades for this specific model, the only way to run Android 8.0 is through unofficial custom ROMs. The Reality of Official Updates oppo f3 android 8 update download
There are no plans for an official Android 8.0 Oreo or newer update for the Oppo F3. How to Check for Official Software You will need to flash a tool like
The latest stable official firmware remains based on Android 6.0 (ColorOS 3.0). How to Check for Official Software The latest
The device will automatically check the Oppo Update Servers for any available OTA (Over-The-Air) packages. If an update is found, tap . Running Android 8.0 via Custom ROMs
You can find community-maintained versions of or AOSP-based ROMs on forums like XDA Developers . Note that these are "Stock Android" experiences and will not feature the ColorOS interface you may be used to. Risks and Warnings