The steps connect to the motor via a swing arm. You can remove a cotter pin which hold a metal bar in place - when you remove the metal bar the steps should swing free. With the steps disconnected you can apply 12 volts to the motor and see if the motor energizes and the swing arm moves. I just jammed a small wire attached to 12 volt battery into the connectors.
FYI - When steps move in/out on there own that is often a sign that you have a low battery or loose wire. Make sure the battery is fully charged, clean/tighten the battery connections, and make sure the grounds are clean (common issue as they are exposed and get corroded).