You will need the larger attachment screw included with the Dynamics Cart and Track System Fasteners for Force Sensor and Accelerometer, order code DTS-ACC, $9 or the one included with Dynamics Cart and Track System, order code DTS, $269.
See the photos below for the correct setup. To assemble, place the Go Direct Force and Acceleration on the cart so that the holes in the sensor line up with the cylindrical brass screws on the cart. The mounting hole of the sensor should line up with the appropriate threaded hole in the cart.
Insert the large attachment screw into the mounting hole and threaded hole, and tighten.