first you need to unlock your bootloader
so go to htcdev.com and follow those instructions, it's pretty easy..once you're done with that, the bootloader will be unlocked.
I downloaded the TWRP recovery img
http://techerrata.com/browse/twrp2/m7
and used
http://forum.xda-developers.com/showthread.php?t=2242635 to flash it. (flash recovery, your own recovery), cmd prompt will pop up, simply "x" that out, another window should pop up and navigate to where you saved the recovery img, and open it...it'll flash the recovery.
After that, boot your phone into recovery, wipe davlik cache/cache/data and then install the custom ROM of your choice.