ANSWERED Before you begin, keep in mind these two points:

The timer runs fast, so the minutes go faster than actual minutes.
The temperature will rise during the experiment. If the temperature gets very high, lower it to around 300 K.
Follow these steps, and then record your observations:

Locate the orange reset button on the bottom right side of the screen.
Press reset to start the reaction over.
Drag the top of the ruler upward until it reaches the 40 mark.
Drag the left platform upward until the top of the platform coincides with the 30 mark on the ruler.
Toggle the blue play/pause button to the play position at the bottom of the screen to ensure that the reaction doesn’t start before you’re ready.
Add 50 A particles, and press the play button on the bottom. Immediately start the timer using the play button on the blue box.
At every minute on the timer, pause the simulation and record the number of A and B particles.