The svg files need to be opened in a vector graphics software application such as Adobe Illustrator, CorelDraw or Inkscape (a free and open-source vector graphics editor which runs on Windows, Mac OS X and Linux).
Inkscape can be downloaded free of charge from the Inkscape home page with tutorials available via Help > Tutorials. Several of these tutorials are linked in HTML (e.g. for printing) as Official Written Tutorials.
ANU Staff and Students:
CartoGIS, College of Asia and the Pacific usually run Adobe Illustrator CC training, specific to editing downloaded Asia Pacific MapsOnline files, in April and September each year. To register go to HORUS or ISIS - Course code: GIS007 or GIS008.