You can easily root Galaxy Note 5 on Marshmallow method. This requires TWRP recovery, which is also provided below, along with a full guide to install both root and TWRP.
? Transfer the root kernel and SuperSU file to your Galaxy Note 5.
The Odin and TWRP file should be on your PC.
Step 2. Enable USB Debugging
Step 3. Extract the Odin file. You should get this file, Odin3 v3.10.7.exe
Step 4. Disconnect your Galaxy Note 5 from PC if it is connected
Step 5. Boot Galaxy Note 5 into download mode:
Power off your Galaxy Note 5. Wait 6-7 seconds after screen goes off.
Press and hold this three buttons (Power + Home button + Volume down) together until you see warning screen. Press Volume Up to continue to download mode.
Step 6. Launch the Odin3 on your Pc
Step 7. Connect your Galaxy Note 5 (which is in Download Mode) to PC now Via USB cable. Odin should recognize your Galaxy Note 5. It’s a must. When it recognizes, you will see Added!! message appearing in the Log box in bottom left, and the first box under ID:COM will also show a no. and turn its background blue.
•You cannot proceed until Odin recognizes your device and you get the Added!! message.
•If it doesn’t, you need to install/re-install drivers again, and use the original cable that came with device. Mostly, drivers are the problem.
•You can try different USB ports on your PC too, btw.
Step 8. Load the TWRP Recovery file into Odin. For this, click the AP button on Odin and the select the TWRP file in .TAR format.
Step 9. Make sure Re-partition checkbox is NOT selected, under the Options tab. Don’t use PIT tab either. Go back to Log tab btw, it will show the progress when you hit start button in next step.
Step 10. Click the Start button on Odin now to start flashing the TWRP on your Galaxy Note 5. Wait till installation is finished, after which your Galaxy Note 5 should reboot automatically. You’ll get PASS message as show below upon successful installation from Odin.
•If Odin gets stuck at setup connection, then you need to do this all again. Disconnect your device, close Odin, boot device into download mode again, open Odin, and then select the TWRP and flash it again as said above.
•If you get FAIL in the top left box, then also you need to flash the firmware again as stated just above.
Step 11. With TWRP installed, it is now an easy job to root the device. Reboot into recovery mode to access TWRP recovery.
? Alternate method if you cannot power off your device. Do this if your Note 5 fails to boot properly after installing TWRP, which is not a problem.
Press and hold Volume down and Power button together to force restart the device, and right when screen goes off for restart, press and hold the Home + Volume up and Power button together to access TWRP recovery you had just installed. You would see TWRP written upon doing this correctly. If not done properly, device will try to reboot normally and you will see Samsung logo instead of TWRP.
Step 12. In TWRP, tap on Install button, and then select the kernel file. Then do the swipe action at bottom to install the kernel. Tap on Back button to go back to main screen of TWRP.
Step 13. Now, install the SuperSU file the same way you installed the kernel using the install button.
Step 14. Tap on Reboot System button to restart your Note 5, which will now have root access on Marshmallow build N920CXXU2BPB6. Your PB6 build is 100% rooted now.
? That’s it. Enjoy the TWRP and root access on your Galaxy Note 5