How do you zoom in on a Mac?

To enable zooming select the Keyboard and Mouse option in System Preferences and then select the mouse tab. Click the box next to Zoom using scroll ball. Select the Options button to configure how you want to zoom.

If you what to zoom in ,or out you have to hold down the control key while scrolling up to zoom in then to zoom in scroll down.

if you have a mac lap top its pretty much the same thing,but after you press the control key you have to hold down the clicker and scroll up or down with 2 fingers to zoom in or out

Turn ON ZOO, Click box then click triangle to open
Click on or near an icon on the screen.
OPTION--COMMAND -- will minimize the screen (minus key)
OPTION--COMMAND = will maximize the screen (equal key)