Nokia Lumia 900

Find "change password"

Press arrow right to open the main menu.

Find "change password"

Press Settings.

Find "change password"

Press lock + wallpaper.

Find "change password"

Press change password.

Change phone lock code

Press the field below Current password and key in the current phone lock code.

Change phone lock code

Press the field below New password and key in a new phone lock code.

Change phone lock code

Press the field below Confirm password and key in the new phone lock code.

Change phone lock code

Press done.

Exit

Press the Home key to return to standby mode.