You have to download a custom rom like Viper or ARHD. Notice that you have to get the right recovery to flash diffrent roms. When using ARHD you have to use TRWP 220.127.116.11 recovery!
So make sure you are using the right recovery.
Some custom roms need to flash the boot.img via command prompt / terminal
Don't forget to hit Thanks Button
HTC One (M7)
ROM: Android Revolution HD