SuperUser, as the name tells is an app that has administrative privileges for granting and blocking other apps to core functions that cannot be accessed otherwise on unrooted devices due to the security of Android OS.
If you want to enjoy all the perks of a rooted device you will need to install a superuser app. The most common, lite and powerful app is the default SuperUser app that comes installed when you root. But you install a different SuperUser app via Play Store or flash the default app if it is missing from the app drawer.
How to flash/install SuperUser on any Android Phone/tablet ?
If you have not downloaded the One X root and fastboot tools folder you can download it here
Copy the SuperUser.apk file to your Phone via USB
Run the file and follow the instructions, this will install the SU (Super User) to your device.
Connect to the internet and update the binary by opening the app and navigating to menu.
You have the updated version of Super User on your android device