If you need to zoom in or out of the canvas, you need to use Zoom Controls located below the canvas.
Option 1: Use the Zoom Controls Slider
You can drag the slider to zoom in and out.
Option 2: Use the Zoom Controls Presets Menu
You can click to select a new percentage,
or Fill Height, to fit the maximum canvas height,
or Fill Visible, to fit the maximum visible area.
Option 3: Use the Mouse scroll wheel
On a Mac, with no asset selected, hold down the CMD key while using the mouse scroll wheel
On Windows, with no asset selected, hold down the CTRL key while using the mouse scroll wheel
Option 4: Use the Keyboard
On a Mac, hold down the CMD key and press the + or - key in the number pad or top number row.
On Windows, hold down the CTRL key and press the + or - key in the number pad or top number row.