I copied this info from another thread:
You push superuser.apk over to the phone using ADB to root (super easy). Then you just download the custom recovery image and flash it using Flashify from the Play Store. The process is actually quite a bit simplier then a Nexus even. It doesn't require erasing everything on your device either.
My bootloader is locked but it has TWRP and is Rooted on stock rom. I haven't flashed a custom rom yet, but I've flashed a few mods, bootanimations, and backups.