An official build is available for v480. To download it, just go to LineageOS official download site.
If you are already running an unofficial build (or a CM build), you must flash the experimental ZIP first. It will prepare your device to receive the official signed update. After flashing experimental, boot once and you can then reboot to recovery and flash the last nightly. By doing so, you can migrate from unofficial to official build.
Or you can just wipe all your data and flash the official build directly. 🙂
After flashing the official build, you can install the next updates via OTA.