The Android One is Google's attempt at taking the emerging market by storm. Google released Android One as an entry level smartphone to give the rest of the world to run the latest version of Android. One of the biggest features is automatic Android updates for 2 years. Google just released and is currently rolling out Android 5.1 to Nexus devices. The OTA has already started to roll out to Android One devices as well. If you have yet to receive your Android One OTA no worries, the files have been captured and you can now download and install the update for your device manually.
To Install:
1. Place the zip on your device's sdcard
2. boot into recovery
3. flash the ota.zip
4. reboot the device (be patient first boot takes a while)
5. enjoy!
Don't worry about factory resetting your device prior to installing. This is an OTA and you will be able to keep your data. Grab the update for your Android One device from the link below.
Via XDA