Find "Change Device Password"
Slide your finger down the display starting from the top edge of your phone.
Press Settings.
Press Settings.
Press Security and Privacy.
Press Device Password.
Press Change Device Password.
Change phone lock code
Key in your current phone lock code and press OK.
Press Password and key in a new phone lock code.
Press Confirm password and key in the new phone lock code again.
Press OK.
Exit
Slide your finger up the display starting from the bottom edge of your phone to return to standby mode.