Oppo F1s, Oppo R9 and Oppo R9 Plus owners can now enjoy Android 6.0 Marshmallow, its new features, updated ColorOS, performance enhancements and dual-SIM function with 4G+3G compatibility (for Oppo R9 and Oppo R9 Plus). Users will get the Marshmallow OTA (over the air) update on their Oppo F1s, R9 and R9 Plus in the coming weeks. If you cannot wait for the OTA update, you can install the update manually.
To install Android 6.0 Marshmallow update manually on your Oppo F1s, R9 and R9 Plus requires at least 1.5GB free space on internal storage or SD card. Since the manual installation process factory resets your device, you should backup every data you have stored on the phone before proceeding. In addition, your phone should have enough battery charge (above 50%) for smooth operation.
After updating your phone to Android Marshmallow, you can experience features like Doze battery saving feature, new improved App permission system, latest security patches and you will also feel performance enhancement.
Before proceeding with the manual installation, check for the OTA update by going to Settings > About Phone > System update. If update found, download and install. It is the safest method and it will not wipe your device
Note: backup every data before proceeding with below steps.
2. Transfer the firmware zip file to root of your phone’s SD card or Internal Storage (require above 1.5 GB freespace)
3. Unlock your phone, navigate to Files > All files > (tap SD card if you have downloaded the package to SD card) > select the zip file > tap Update now.
4. Your phone will then reboot and start installation process. (Do not do anything on the phone or power off it during the process).
5. Once the process is completed, your phone will reboot and remain on the Oppo logo for 3 to 5 minutes (Do not power off the device)
Now, set up your device and enjoy Android Marshmallow. To get dual SIM function on Oppo R9 and Oppo R9 Plus, go to Settings > Dual SIM and mobile network > Preferred network type and make sure you have selected 4G/3G/2G (Auto) as Preferred network type. (Source – Oppo)