Get My Image to Fit Fully on the Screen?

My favorite way is to just double-click on the Hand tool in the Toolbox, but you can also press Command-0 (zero; PC: Ctrl-0), if you prefer to use a keyboard shortcut. Also, if you switch to the Hand tool (the shortcut is the letter H), you’ll see three buttons up in the Options Bar for zooming the overall image: (1) 100%, (2) Fit Screen, and (3) Fill Screen. You could go under the View menu, as well, and choose the size you want manually, but . . . don’t waste time digging around in menus, just use one of the first two methods.