Performing a factory data reset on your Samsung Galaxy Young SCH-i509 via External keys of hardware buttons. In case you can not do it from settings menu. Using this combination of button you can entering Android system recovery:
Entering android system recovery and performing factory data reset
Press dan hold Volume Up button and Power Button simultaneously till the screen turns up and Samsung logo blinks for two times. Then release the power key but keep the Volume Down key pressed till you see 2 icons. It will enter Android system recovery.
In the Android system recovery mode use the volume keys to scroll the list or highlight an option and the Home button to select it.
To perform a factory data reset, select wipe data/factory reset and press home key.
Only do this if you can not do it via Setting menu.
Warning! All data will be erased from device memory, including system and application data, settings and downloaded applications. Back up your important data. The device will restore to factory settings.