Move: drag a part. When its holes come close to another part's holes, it snaps on with a yellow ring.
Bolt + nut: point at a hole and click. A bolt and nut go through every hole lined up there, and the parts become one assembly.
Wheels, gears, pulleys: drag one to the end of a motor shaft or axle. It turns to face the shaft and slides on. The yellow and red wheels fit the BO motor; the grey wheel, gears and pulleys fit the 6 mm shaft of the geared motor and the axle.
Ball caster: drag it under any strip or plate. Its two holes are 20 mm apart, so they line up with any two holes one apart. It always goes underneath, ball down.
Geared motor: drag its threaded neck into the big hole of the motor clamp from either side, then bolt the clamp to your frame. The nut goes on the shaft side.
Gears: set two gears side by side on parallel shafts so their teeth touch. With the power on, the driven gear turns the other one.
Wires: pick the Wire tool (W), click a terminal (the coloured pins on motors, the battery, the switch and the controller), then click another terminal. Red wires go to +, black to −. The Spanner takes a wire off again.
Circuits: with a battery on the bench, a motor only turns when both its pins are wired back to the battery, through the switch or the motor controller. Swap the two wires and it turns the other way. With no battery on the bench, Power simply runs every motor.
Motor controller: wire the battery to BAT+ and BAT−, and each motor to A1/A2 or B1/B2. Select the controller to set each channel to forward, stop or reverse and change its speed.
Camera: drag empty space to orbit, scroll to zoom, right-drag to pan.