If you want to know much more about the Windows environment
  than is covered in this manual, you might like to buy some of
  the many books about Windows (e.g. by Petzold, or Schulman).
  You might even buy a copy of the Windows SDK (Software
  Developer's Kit).
  
  If you do, you'll see that Clip-4-Win provides straightforward
  access to many of the facilities provided by Windows.
  
  Should you wish to access facilities that are not available in
  the current version of Clip-4-Win, you can do so in most cases
  using CallDLL(), with the related functions LoadLibrary(),
  GetProcAddress() and FreeLibrary().

  As an alternative, you can use the Clipper Extend System.
  Note, however, that any Windows function whose name is ten
  (10) or fewer characters long has been renamed by prefixing an
  underscore (_).  As an example, Polygon() has been renamed
  _Polygon().  This is to allow the unprefixed name to be used
  in PRG files.

  The samples in source\winapi should help you.  For example, if
  you want to use resource menus you can use the
  source\winapi\menu.prg functions to manipulate them.