TWRP stands for team win recovery project and it allows the Samsung Galaxy Note 4 users to easily flash custom firmwares easily. After installing TWRP on your Note 4, all you will have to do download the ZIP file containing the firmware or hack to the phone and flash it in recovery mode by holding down the volume up + power button.
It shall be noted that the warranty will be void after you have installed TWRP custom recovery on your Samsung Galaxy Note 4. You can download it from following links: