There are two buttons at the bottom of the Help window,
  labeled Go Back and Exit.

  Clicking on the Go Back button displays the previous
  topic. This is useful if you want to review something,
  or if you find that you have taken the wrong path and
  you are not getting the help you thought you were going
  to get.

  Each time you click on the Go Back button, the next
  previous topic is displayed, until you return to the
  first frame. If the topic you want to see is a long way
  back, use the History... menu option from the Search
  menu.