At the beginning, turn off the phone by holding the Power button.Reset SAMSUNG J100F Galaxy J1
Resetting the Phone
Resetting the phone erase all data, including downloaded applications, and resets the phone back to its initial state—the state before you turned on the phone for the primary time.
Important be sure to back up essential data you have on the phone before you reset your phone. You can back up your important data like application, image and etc by sync with a personal computer.
To reset the phone
1. Push HOME > MENU, next tap Settings > Security > Factory data reset.
2. On the Factory data reset screen, tap Reset phone and after that tap erase everything.
To reset the phone using phone buttons
1. With the phone turned off, push and hold the HOME and BACK buttons, and after that briefly press the END CALL/POWER button. The reset process will begin after a few seconds.
2. Wait for the phone to come to an end the reset process and then push MENU.
Tip: if your phone hangs for long time or freezes, remove the battery then wait for a few seconds, and then re-install it. After re-installing the battery, turn on the phone. Your problem solved.