CM13 aka CyanogenMod 13.0 for Samsung Galaxy Note 4 has been released. Right now, only N910C and N910CQ are supported. Also keep in mind that this will make your device out of warranty and increase KNOX counter as well. But if you are out of warranty and feel free to proceed.
1) Make sure you have TWRP 18.104.22.168 on note 4. Download ROM as well from here.
2) open Recovery Mode on device. ( Home + volume Up + Power)
3) Do a full wipe. (Data + System + Cache + Dalvik Cache)
4) Select "cm_treltexx-ota-765ef3442c.zip” file when start a setup.
5) When it finish process, you reboot your device.
6) process completed.
While this CM13 release is deemed as stable, we still suggest sticking to stock if you are looking for more stable experience. CM13 brings android 6 marshmallow to the Note 4 and there is nothing better than CyanogenMod 13.0 to enjoy android 6.0 on note 4.