In TWRP‘s main menu, go to Backup . Select all partitions (System, Data, Boot) and swipe to back up your current operating system. If anything goes wrong, you can restore this backup and return to your old setup exactly as it was.

Move the ROM ZIP and GApps ZIP to your phone’s internal storage.

: While these are 7.1.2, they are fully compatible with 7.0 and often more secure.

Swipe to confirm. Do wipe "Internal Storage" if your ROM zip is stored there. Flash the ROM : Return to the main menu and tap Install . Navigate to your ROM .zip file and select it. Swipe to confirm the flash. Flash GApps (Optional) : Immediately after the ROM is finished, go back to Install . Select the GApps .zip file and swipe to flash. Finalize & Reboot : Once both are installed, tap Wipe Cache/Dalvik if prompted.