How to place more than one marker on the map?

Currently Cargo's map element does not support multiple markers. You need to customize Cargo's plugin a bit to achieve this. Please edit bt_gmap.js in your Cargo plugin's folder (usually /wp-content/plugins/cargo/) and find the following statements:

var marker = new google.maps.Marker({
 position: myLatLng,
 map: map,
 icon: icon
 });

In order to add another marker please add the following just below the referenced statements:

var myLatLng = new google.maps.LatLng( 41.7144678, -75.015827 );
 var marker = new google.maps.Marker({
 position: myLatLng,
 map: map,
 icon: icon
 });

where 41.7144678 and -75.015827 are latitude and longitude. Please adjust them according to your needs.

For additional markers just repeat the procedure above.