First Method:- Menu Settings.

home screen please select Apps > Setting > General -> Backup and reset -> Factory data reset
Reset device if you have password, please enter it, and tap Delete all.

Second Method:-

your phone is switched off.
now press and hold Volume Up button + Home button then press Power button.
Hold them down until you see Samsung logo appears, then release Power button only.
When you see green screen release all keys.
On the menu select option "Wipe Data / Factory Reset" using Volume Down button and confirm with Power button.
Next use the Volume Down button again to select “Yes — delete all user data”.
Please confirm this operation with Power button.
When the operation is over select option "Reboot System Now" and confirm with Power Button.