All the source code for Lineage OS is available in the Lineage OS Github repo.
* Reboot into recovery
* Wipe data, system and cache if it's a fresh install (any rom which is not official Lineage, including Cyanogenmod).
* No wipes required if you're updating from a previous official build of Lineage (wipe cache and dalvik cache recommended).
* Flash ROM and, optionally, Gapps and Root. Reboot.
* OfficialROM: https://download.lineageos.org/v521 [nightly]
* Gapps: Open GApps
* Root: https://download.lineageos.org/extras [su (arm)]
Source Code: https://github.com/LineageOS
Last Updated 2017-04-28