If you like to tinker with things on your Android device than you will most certainly need a custom recovery installed on it. One of the most popular custom recoveries out there is TWRP from Team Win, otherwise known as Team Win Recovery Project. Having the custom recovery there allows you to do things like make backups of your device image should anything go wrong, so you can always revert back to the saved image before issues persisted. The custom recovery is also your launchpad for installing and flashing ROMs and other apk files or device system tweaks that can only be installed by flashing.
Two of the newest devices to get support for TWRP today are the Samsung Galaxy Note 4 on T-Mobile's network, and the Samsung Galaxy Note 4 on Sprint. Both these devices have not been out long which makes it pretty impressive that TWRP is already available, meaning that Team Win has been hard at work getting TWRP ready and compatible with this device. If you own a Galaxy Note 4 on either of those networks listed above, make sure to do any solid backups of stuff you might want, and then read up on the process of flashing a custom recovery if this will be your first time doing so.(Some handy guides can be found at XDA for your specific device)
Team Win has you covered on the download files of TWRP for both devices, you can find the stuff you need at their posted page at the source link below. As Team Win states, there are three methods with which to proceed, which includes flashing the recovery using ODIN, this is a Samsung device after all, or you can use the DD method which uses adb or the terminal emulator to install. There's also a flashable zip process, if you're already familiar with flashing files to your device and such this might be the easiest way. If you're planning on putting TWRP on your Galaxy Note 4 for Sprint or T-Mobile, let us know how the process goes and share your thoughts on whether or not you have used TWRP before on other past devices. Do you own a Galaxy Note 4 for T-Mobile or Sprint? How do you like it so far? Let us know in the Google+ comments.