Prerequestis :
-Before doing anything you have to backup your Samsung Galaxy Note 5 Data See this guide here
1-You need to enable USB debugging mode which is deactivated by default. (you can skip it ) 2-Your Note 5 should have 70-80% charge remaining.
3-USB Cable to connect your phone with your PC .
Step by step root for Note 5 :
1.First find out which variant of Note 5 you have.
You can find it withSettings-About device-Model number.
Here you will see exact model number. (This may be different from original if you have flashed a ROM with different variant. Like your device is N920C and you have flashed a ROM for N920I, this will display N920I. But here we are assuming users reading this guide is non rooted and stock ROM users so it will be same as original variant)
2.Unlock Flashing
Go to settings-about device-Software info - You will see "build number" - Tap repeatedly on build number to unlock development optionNow you will see Development option in setting (just above about device)Open Development option - OEM Unlock - Enable it.
3.Flashing custom Recovery.
Download TWRP by @bigbiff according your variant. Here select tar version of file NOT zipORPhilz CWM. Philz recovery is ported for Note 5 by @arter97 and you can download from his web page. - Here look to latest build and select your device model. for example your variant is N920I you have to open n920ci (this indicate n920c and n920i) and download Philz recovery with file name ending tar.md5 (not zip)
4.Flash custom recovery.
Use Odin V3_10.7 to flash downloaded recoverySwitch off device
Reboot to download mode : (Vol up+power+home)
Select downloaded above said Philz recovery with AP tab of Odin and flash.Reboot to recovery and now you should have custom recovery.In case still you have stock recovery then follow thisAgain reboot to download modeSelect recovery file with AP tab of OdinNow uncheck Auto reboot optionFlash selected fileOnce flashing complete, disconnect device and long press Vol down+PowerOnce screen turns off, immediately press vol up+power+home to reboot to recovery manually.
5.Flash custom kernel For Note 5
Download custom kernel according your variant and flash from recovery.Here available custom kernels-Nobel Kernel-SkyHigh
6.Now flash Beta SuperSU 2.49 zip from recovery.
Now DON'T FORGET TO MAKE EFS (IMEI) BACKUP
Check now that your phone rooted with root checker APp Here
Source : XDA , TWRP