You can copy any area from any part of the screen into the Icon Editor. You can copy ("grab") a text or graphic that is displayed and load it into the Icon Editor work area.
Save your current icon, if necessary.
Choose Grab Screen Image from the Edit menu.
Drag a box around the portion of the workspace you want to capture (press mouse button 1, drag, and release).
Capturing a region of the display could cause the icon to use up some of the available colors on the desktop.