[X Style (Pure) Q&A, Help & Troubleshooting] jason2678:
One piece of advice for starters just since you used the word noob. Never mod your phone on a low battery. You can mess a phone up enough to break offline charging, and without a removable battery that you can swap out or charge in a cradle that could get awkward in a hurry on this phone. I always make sure I'm >75% just in case. You can fastboot your way out of all kinds of trouble; but not if your battery is dead and your phone is so screwed up it is not offline charging.

Your phone will probably show up with Android 5.1.1 installed, at least I got mine about 3 weeks ago and it did. Once it is through initial setup it should want to apply an OTA to Android 6.0 right away; if not check for it in Settings -> About -> System updates and it should find one. Just let it update before you do any setup or app downloading.

Once you're on MM, before you do any setup you have to unlock your bootloader if you intend to root. You'll get all the warnings about voiding warranty and here there be dragons, so be prepared for that. Also, unlocking the bootloader will wipe your internal storage, so don't bother with any setup or app downloading before you do it.

Start with Heisenberg's thread. It is a great guide on how to setup your computer for adb and fastboot as well as all the syntax you need for unlocking the bootloader and installing a custom recovery. Make sure to get the 2.8.7.1 version of TWRP that is patched to work with the MM bootloader.

When you boot to TWRP recovery for the first time it will ask if you want to keep system read only. Keep system read only and make a backup immediately. I usually make one backup of boot, system, and data, and a separate one of just efs; don't worry if you don't understand, you'll figure it out when you get there. TWRP is all touch based and pretty intuitive. This way you have good, untouched system backup to fall back on just in case.

When it comes to rooting MM, don't use the old system install method. Flash a SuperSU from this experimental systemless root thread (I used this instead of the ivcarlos method linked to the Heisenberg thread because it is more automated and easier). I can vouch for the 2.62-20151210170034 version of SuperSU. I've used it to root stock MM on this phone 3 or 4x as I've restored backups and changed kernels. I've heard the 2.64 and above SuperSU versions are not working with this phone on MM, and the older traditional system root methods like the v2.49 version that is linked to the Heisenberg thread are causing bootloops on MM. Don't panic on first boot after the systemless root; it appears to bootloop once but comes up normally the second time.

One other thing, TWRP doesn't seem to be able to detect the systemless rooting method, and it really wants your phone to be rooted. If/when TWRP offers to automatically install SuperSU, don't let it - ever - it will keep asking. It must use the old method that causes bootloops on MM, not the new systemless method linked above.

Once you're all rooted and settled in, if you get sick of the unlocked bootloader warning you can fix it by reading up in this thread. Just be sure to read carefully and get the MM logo and not the LP logo.