It took me a while to figure that out. It may be different on all computers, I don't know…On mine though, I selected Preview from my applications, clicked on 'File', and scroll down to 'Take Screen Shot', then you can choose to take from the window, selected, or entire screen. Once you take the shot 'Save' it and then come back here to 'upload'.
Gee, now it all sounds confusing again.
Basically I just 'played around' until I figured it out.
