If you want to zoom within your project, simply use the zoom percentage option at the bottom of the screen. Alternatively, you can also use pinch-to-zoom, by touching two fingers on the touch screen or touchpad and moving them apart to zoom out, or together to zoom in.
You can also use '+' and '-' on your keyboard as shortcuts, or 'Shift' + 'Scroll up or down.'
In order to navigate among your projects, simply click on the space bar, and drag your cursor around the screen. You can also use two fingers on your touchpad to navigate the screen.
For this to work, your cursor must be on the black or white background, rather than on one of the screens.