Want to update to lollypop a rooted Twrp installed and bootloader unlocked mobile

Hii guys sorry if I post it in wrong place. I was unlocked the bootloader recently by htc dev and install twrp... Then I flashed SuperSU to gain root. Now an update come of 990 mb of size and this is clearly mention that this is lollypop update. My mobile is S-ON. I want to update my mobile to lollypop but don't want to become a brick maker. :).... So pls guide me.... My mobile is htc desire 820 Indian version