Just a simple daily quick tip from me on how to enable or disable installation of non-market apps on Samsung Galaxy S III (SGS3). There’s nothing weird about how to make it done and I think the way it’s done is pretty common. Just in case you are still confused on how to allow installation from unknown sources.
How To Enable Unknown Sources
1- On your phone, tap on “Settings”
2- Now scroll down a bit and tap on “Security” (under Personal section)
3- Again, scroll down a bit
4- Find a section named “Device Administration”
5- Go ahead tick the “Unknown Sources” to enable it.
That’s it. You can also watch a video demo how to do the trick..