Need to upgrade from Android ver. 4.4.4 to Android ver. 5.0 with unlocked bootloader

I have an Xperia Z and recently I unlocked the bootloader.
However now I cannot install (upgrade) to the Lollipop Android 5.0 (10.6.A.0.454) from Android 4 (10.5.1.A.0.292).
Please advise on a step by step process since I am not experienced.