If you don't have a graphics program, an easy way is to ALT + PRTSCN the screen you want to capture, then CTRL + V in a Word doc. When the image pastes to the document, right click on the doc and select Save as Picture. In the window that pops up, be sure to select the type of file (I think PNG is default but you should be able to choose JPEG or a handful of other options). Also, choose where you want to save the pic, and click Save.