A full system backup is critical as this process wipes all data.
The Oppo F1s originally ran Android 5.1 (Lollipop) and officially received an upgrade to Android 6.0 (Marshmallow) with ColorOS 3. OPPO India Community Update software – OPPO F1s - Android 5.1 Guide Oppo F1s Firmware Download 7-1-2
Move the downloaded ROM and GApps .zip files to the root directory of your device's internal storage or SD card. A full system backup is critical as this
