Press and hold until the Oppo logo appears to enter Recovery Mode. Select your language (English). Select Install from storage device -> From SD card .
Flashing the wrong firmware can permanently damage your phone. The Oppo F1s has several regional variants. firmware oppo f1s a1601
To check the firmware version on your Oppo F1s (A1601): Press and hold until the Oppo logo appears
Warning: This will wipe all data.
Most regions peaked at Android 6.0 Marshmallow . No official updates to Android 7.0 or higher exist. firmware oppo f1s a1601
Locate and select the firmware .zip file you transferred earlier. Tap or Yes to confirm the installation.
The industry standard for MediaTek devices.