I see how to enter help text for a Microsoft Word form text box or drop down, but then how does the user view the help text when they are completing the form?
There are actually two types of help you can add to a form field, corresponding to the two tabs in the dialog you get when you click the Add Help Text button in the form field's Options dialog:
The first tab is titled "Status Bar", and the text (or AutoText entry) you specify will appear on the status bar at the bottom of the Word window when the cursor is in the field. It should be something short.
The other tab is titled "Help Key (F1)". If you specify text (or an AutoText entry) here, it will appear in a message box when the user puts the cursor in the field and presses the F1 key. This can be longer, on multiple lines if needed.
You can add both kinds of help to the same field if you want. For example, the status bar help could say something like "Address: press F1 for help", while a longer description is in the F1 help.