Do you mean you want to add a point by coordinates?
If so you can just add them to the shapefile by creating a new shape, add points to this shape and add the shape to the shapefile.
Here's an example:
http://www.mapwindow.org/documentation/mapwingis4.9/_create_point_shapefile_8cs-example.html#a5
If so you can just add them to the shapefile by creating a new shape, add points to this shape and add the shape to the shapefile.
Here's an example:
http://www.mapwindow.org/documentation/mapwingis4.9/_create_point_shapefile_8cs-example.html#a5