Installation steps:

• download rom zip file.
• Reboot to recovery
  • flash rom.zip
  • flash TWRP as recovery Ramdisk
  • Reboot to recovery .
  • wipe data partition
  • reboot to system

Note :- if you are encrypted and can't access internal storage copy Rom Zip in Pendrive and use OTG to flash

First boot after an install or update may take some more time but don't worry.