Finally, OnePlus has released OxygenOS 2.1.4 for OnePlus One, which offers new features, clean and unburdened user experience. This version of OxygenOS is a full firmware package, so it is not available via OTA (over-the-air). You will require flashing the firmware manually. The below guide explain how to update OnePlus One to the latest OxygenOS version 2.1.4 manually.
Due to hardware limitations, not all features of OnePlus 2 are included in the OxygenOS version 2.1.4 for OnePlus One, such as manual camera mode, MaxxAudio and screen temperature slider. However, owners of OnePlus One can enjoy all other unique features of OxygenOS like Dark Mode, custom icon packs, App permissions, double tap to wake and all other gestures.
Before you start installing the OxygenOS 2.1.4, please note that DO NOT flash this build through TWRP custom recovery. You will most likely lose your radio and IMEI number, which means, you will not be able to use your phone with any network.
a) Your OnePlus One should be running on OxygenOS or Cyanogen OS12 and above.
b) Driver for OnePlus One installed on your computer (Windows)
c) At least 50% battery charge remaining.
d) ADB and Fastboot drivers are installed in your computer. See this article [HERE] for details.
e) Backup every data on your phone
Disclaimer: Follow the instruction at your own risk. We will not be liable if any damage occurs to your device and/or its components. It is recommended for technically talented users only.
2. Unzip the OPO 2.1.4 Patch.zip file (use 7zip) and save the contents inside the ADB installation folder.
3. Boot your OnePlus One into Fastboot mode. To do so, switch off the phone, press and hold Power and Volume Up button together.
4. Once entered into fastboot mode, connect your phone to your computer (Windows), go to the ADB installation folder and click on ‘allinone.bat’ file.
5. In the command prompt window, select 1 to check the connection status. You should see your device ID in the window.
[If you do not see the device ID, you should install proper drivers for your OnePlus one on your computer]
6. Now, select 2 in the command window and your device may reboot. If it does not reboot skip to step 7, else go to step 8.
7. Skip the setup process on your phone.
8. Press 5 on the command window and hit enter and your device should boot into existing OS.
9. Now, transfer the downloaded OxygenOS 2.1.4 zip file to your phone.
10. Then boot your phone into fastboot mode. To do so, disconnect the phone for your PC, power off it, press and hold Power + Volume Up keys.
11. Connect the phone to your computer and enter 3 in the command window.
13. Now, select 4 to boot OnePlus One into stock recovery. If not, press and hold Volume Down + Power Button.
14. In stock recovery, select your language, select ‘Wipe data and cache’ and perform it.
15. Once done, select ‘Install from local’, select the ROM zip package, select -> Yes -> Install -> Yes -> Reboot and then select ‘Reboot’ again. Your OnePlus One will boot into OxygenOS. (Source)