Here is a little quick guide to how I managed to put a ROM of my choice onto my HTC One.
Preparation
Download the ROM(s) you are wanting to use. Once downloaded, drop the .zip onto the phone memory, anywhere you wish.
Do this first as it makes it much more straight forward for later.
Back-up everything you want. As it will be lost as soon as the bootloader is done.
Unlocking the bootloader
The bootloader. Following his instructions make it simple, and his download is clean. Watch how he starts his phone into bootloader mode, as this is used throughout this process.
Recovery
Then, it is the recovery step. I used the tool you can find
here.
On there, you follow the instructions on the right hand side, and I would recommend using CWM (Clock Work Mod) for the recovery step. It is very easy to use.
Installation
Once the recovery is done, you can restart the phone & use recovery mode this time, rather than fastboot as you will have been using previously. Select to load the rom from the internal SD card, and then find the .zip file. Once you have selected it, please be patient. Once this has completed, your phone will load up with its new rom installed.
*This guide is my attempt to help. Follow at your own risk!
