When it comes to rooting, custom recoveries, custom roms, custom kernels, and so on I recommend heading to the xda forums. There are many great guides and tools for a beginner. I have linked a few pages for the HTC One M9 below. Hope they are helpful.
http://forum.xda-developers.com/one-m9
http://forum.xda-developers.com/one-m9/general/guide-root-install-twrp-htc-one-m9-t3061133