Before first use, purchase and then insert 2 fresh AA batteries (LR6) into the compartment, with the correct polarity (+/-).
To build the motor into a K'NEX model, simply push a classic K'NEX rod (quite hard) through the hole in the middle. Experiment by turning on the switch on the battery pack to turn the rod in each direction.
The easiest way to attach the motor to your model is to fit an 8-way connector onto the lugs at each side of the motor, as shown in the photo opposite.
Finally, read Hint W6 if you want to make your battery motor turn wheels or connectors.