As other, newer devices have gotten Android 5.1, the Nexus 4 hasn’t gotten that update yet. Now though, Android 5.1 can be downloaded OTA.
If the update doesn’t show up for you in your settings, you can download it from this link. Once you have downloaded it, you can read how to install the update here. Enjoy the new features that Android 5.1 brings.
Via: Droid Life