I recommend giving short, basic introductions to the main topics, oversimplifying if necessary. For example, to explain how press works, give a very simple example of how to send press to France. In particular, one player thought that press to gm would do it. A simple, basic example will get them started. Once they've internalized the simple case, the rest of the HELP file will be vastly more comprehensible.
Similar remarks apply to order syntax.
Giving an example of a move order, and a convoy order, and a support order will prove much more helpful than the big help file for syntax . The main thing to explain here is the NEXT parameter. I bet few GM's do. Suppose the NEXT parameter is set to 72 hours. The short, sweet explanation is that everyone starts with a dedication of zero, gains 3 points every time he or she submits a move on time, and loses a point for every lateness day.