2. Install TWRP recovery (use Hasoon toolkit)
3. Get in TWRP > Backup > choose Data, System, Cache. Thats call Nanoid backup. Store that on your computer just in case you want to go back to stock ROM.
4. in TWRP when you reboot the phone, it will ask you to install SuperSU. Accept. Boot the phone, find SuperSU, open it up & follow on screen instruction to have root.
(assuming you've done all that to have root like you said)
5. S-Off using firewater (optional. I always S-off my device when I can. make sure you disable anti-virus program before attempting to S-OFF).
6. Super-CID (search for Vomer's guide on htc one m7) (optional)
7. Download any custom ROM you like. For me, i'm running InsertCoin.
8. Install custom kernal like ElementalX (OPTIONAL). I stay with stock kernel for now.
Enjoy your device with full potential now !!!
EDIT: Search for my most recent post about Viper4Android. You'll be WoW !!!!!!!