Adding markers to google map

I’ve used the WP Google Map Settings to create a map specifying the zoom, lat, long,width, height and created a shortcode [map_locations] which I’ve placed on the page I want. the map shows up fine but I can’t see where it is that I can add markers to the map.

Under the locations heading in WP there doesn’t appear to be an info message box field. It looks like the locations are separate posts. Is it possible to view the page with the maps and markers as a preview?

Thanks for your help

http://ww.wp.xz.cn/extend/plugins/wp-google-map-plugin/