This article describes how to perform a factory reset.
INSTRUCTIONS & INFO
A master reset reverts the device back to factory settings. It will permanently erase all personal data, preferences, settings and content such as pictures, ringtones and apps that are saved to the device. Data stored to an SD card will not be erased unless otherwise selected. It is recommended that you save (backup) important data to your SIM, SD card, or a computer before proceeding.
From the home screen, tap Settings.
Scroll to, then tap Backup and reset.
Tap Factory data reset.
Tap Reset device.
Tap Delete all.
If unable to reset the device using the above steps, try the alternate master reset method by first powering the device off.
Hold the Volume up key + Power key until the Samsung screen displays.
Press the Volume down key 2 times to select Wipe data / factory reset, then press the Power key.
Using the Volume down key, scroll down to Yes - delete all user data then press the Power Key.
The device will reboot and display the recovery screen.
Select Reboot system now then press the Power key to restart the device.