How to Make ICO Files in Photoshop on a Mac. Images that are used as icons in the Windows operating system must be saved in ICO format. By default, Adobe's Photoshop image-editing program does not ...

Open the JPG image file you want to convert into an icon. With the plugin, you merely need to save the file with the file extension of .ico to create the icon.

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, since that's what Windows uses for icons.