Open Macintosh HD or the folder where you want to display the hidden files in the Finder. Hold down the Command, Shift and Period keys: cmd + shift + [.] The hidden files and folders on your Mac will then appear partially transparent.
Command-Shift-3 captures a screenshot of the entire screen. Command-Shift-4 turns the cursor into a crosshair where you can capture an area you define. Command-Shift-5 displays a resizable box on the screen where you can capture an area you define. All three methods save the image to your desktop in the .png format.