For those of you having problems with the latest UVUAMDL firmware, this is because T-Mobile has added a SetUID restriction on the kernel. This can easily be solved by flashing a stock kernel with the restriction removed.
MAKE SURE YOU ARE ON UVUAMDL build OTHERWISE THIS KERNEL WILL BREAK THINGS IN YOUR PHONE!
Then follow the rest of the steps to install CWM SuperSU zip file in recovery.
Credits – XDA <— Please donate to developer or hit “Thanks” button on XDA if this has helped you!
What is a Custom ROM?
A custom ROM is a custom, modified operating system that you can install on your Android device. Basically it's like installing Windows OS on a Macbook. By installing a custom ROM, you can bypass stock factory settings like locked hotspot tether, install new Android versions early, or even convert your phone into another OS.
With a custom ROM, you can really maximize the capabilities of your smartphone by adding custom features that have been developed by open source developers.
How to Install Custom ROMs
First, you will need to root your device, if it is not rooted yet, follow our root tutorial and root your phone.
Once rooted, you should have TWRP installed on your phone. Installation of a custom ROM is easy if you learn the basic of it. If you don't know how to install custom ROMs using TWRP recovery, see our tutorial on How to Install Custom ROM using TWRP!