Final answer:
Zooming in on Tinkercad is done by using the mouse's scroll wheel, which allows for precise control over the viewing of the model.
Step-by-step explanation:
To zoom in on Tinkercad, you should use the scroll wheel on your mouse. By scrolling the wheel forwards, you can zoom in to get a closer look at your design, and by scrolling it backward, you can zoom out to see more of your workspace. This is a common control mechanism in many computer-aided design (CAD) programs, allowing for precise control over your view of the model you are working on.