adb shell -> su: not found
Your device is not rooted.  To see what Rooting is and how to go about doing it: 


http://www.androidcentral.com/root
What does &quot;to root a phone&quot; mean?


Once you have rooted your device, you will be able to access the Super User state of your device (SU). Just be aware that rooting could brick your device if done incorrectly, as could and tampering with files in the root directory.