You can use the macOS Finder's Copy command to copy and paste files. But here's how to use the same command to copy file icons into Preview. You've probably used the macOS Finder's popup contextual ...
You can change nearly any desktop icon on both Mac and PC. To change desktop icons on a Mac, open the "Get Info" menu and paste in the picture you want to use. On a PC you'll need to make a .ICO file, ...