[Q]I have a One M8 with DigitalHigh GPE 4.4.4 installed, how do I update to Lollipop? topic

I have tried installing CM12, but it keeps giving me errors in the recovery. I have tried installing the 5.0.1 version of DigitalHigh GPE, but that wouldn't boot. I've heard about upgrading to 4.4.4 firmware first, how do I do that?