Never display an apparel which had not been steamed nor ironed. If it is necessary to separate the legs so that you can put on the trousers, separate them now. Put on one leg of the trouser on the mannequin. Insert the other leg. Insert the locking device in the receiving hole of the leg.
Some mannequins require twisting either clockwise or counterclockwise to lock the legs together.
Others just need to be inserted and it will lock. You will hear a click if the parts locked correctly. Put on the socks or hosiery. Fix the shoes so that they fit properly, then tighten the screw on the receiver for the rod. Tighten the screw on the mannequin.