Accessing entity data

If I have czml data loaded via CzmlDataSource with several pieces of data:
    {
        "id":"LINE 1",
  "name":"LINE 1",
  "polyline": {
      "width":3,
      "material": {
                "solidColor": {
        "color": {
      "rgba": [255,255,255,255]
        }
    }
      },
  "positions": {
            "cartographicDegrees": [ lat,long,lat1,long1...]
        }
    },
    {
        "id":"LINE 2",
  "name":"LINE 2",
  "polyline": {
      "width":3,
      "material": {
                "solidColor": {
        "color": {
      "rgba": [255,255,255,255]
        }
    }
      },
  "positions": {
            "cartographicDegrees": [ lat,long,lat1,long1...]
        }
    }

How can I retrieve the lat/long from this data? It's not clear how to access data once it has been processed. I would like to essentially allow the user to draw a shape on the globe, and have the application do analysis on the lats/longs that fall within that shape. (The entire polyline may not be included in the shape.) But I'm having trouble retrieving any info, let alone position data.

I have tried:
    var mySource = new Cesium.CzmlDataSource(“MyCzmlDataSourceName”);
    function displayData() {
        mySource.entities.removeAll();
        //the first “entity” is selected, but not displayed,
        //and none of the other entities are displayed,
        //this is not the expected behavior
        mySource.load(‘http://path/to/my/data/myfile.czml’).then(function(){
            viewer.selectedEntity = mySource.entities.values[0];
            alert(viewer.selectedEntity.label.text); // <--displays “[object Object]”
        alert(viewer.selectedEntity.label.text.getValue(JulianDate.fromDate(new Date()))); // <--still nothing, I googled and saw something about
           //using getValue, but there isn’t a specific time attached to the data.
        });
    }

I've realized I forgot to add mySource. I've done that and my entities are displayed, however, still not sure how to access data, such as the name, id, positions, etc.

Nevermind, something just clicked and I found my error.

    viewer.selectedEntity = mySource.entities.values[0];
    alert(viewer.selectedEntity.label.text.getValue(new Date()));
    alert("positions = " + viewer.selectedEntity.position.getValue(new Date()));