Unlocked bootloader. If you have not unlocked the bootloader of your HTC One start here.

Rooted HTC One.

Custom recovery, you must use CWM RECOVERY 6.0.4.3 OR HIGHER or TWRP RECOVERY 2.6.3.3 OR HIGHER

Download the HTC One Google Play ROM from here. Download the HTC One Radio for Google Play Edition ROM from here. Transfer both files to the internal storage of your smartphone. Do a full phone backup, apps, data, messages, pictures... You can use Titanium Backup or Go Backup. Make sure you phone is S-OFF, or you might end up with a stuck phone. Reboot the HTC One in recovery mode. Turn off your phone and press Volume Down + Power button. Once in Fastboot mode, use the arrows to select Recovery. When in Recovery, do a full backup just in case you want to go back to the Sense ROM. When the backup is done, go and install the ROM first and after it, the radio file. Reboot your HTC One device and wait for a few minutes, since the first boot may take longer then usual.

If you are not a fan of HTC Sense 5 UI and you wish to have the stock Android 4.4 user experience on your Non-Google Play HTC One you can still install the Android 4.4 KitKat Google Play Edition ROM on your device.After you have successfully unlocked the bootloader and rooted your HTC One, here are the steps to install the Android 4.4 KitKat Google Play Edition ROM on your NON-GP HTC One:If something goes wrong or your phone does not want to boot up, start the process again from step 6.For theAndroid 4.4 KitKat Google Play Edition ROM click here