Defining the x and y coordinates of a Part

I would like to set the x and y coordinates of a Panel within a absolutely sized Diagram. I understand that Imust use an instance of the Point class to do this. However I am at a loss as to how to do this. Is it something like this:

 var myPoint = $(go.Point, {x: 240, y:80})

$(go.Panel, "Horizontal",
 { width: 60, height: 60 , x: myPoint.x, y: myPoint.y}, // panel properties
  // elements in the panel:
  $(go.Shape, "Rectangle", { stroke: "lime" }),
  $(go.TextBlock, "Some Text")
) 

Or maybe I need to Bind the x and y properties to those of myPoint? Sorry for being such a neophyte, I appreciate your help.

Just do:

$(go.Node, "Horizontal",
  { location: new go.Point (240, 80) },
  // elements in the panel:
  $(go.Shape, "Rectangle", { width: 60, height: 60, stroke: "lime" }),
  $(go.TextBlock, "Some Text")
)

Everything is just JavaScript code to be evaluated.

And to add the above node to an extant Diagram, would you simply pass a key in to the Node definition. like this?:

myDiagram.startTransaction("add node");
myDiagram.addNodeData({key: "myKey"});
myDiagram.commitTransaction("add node");
var theNode = myDiagram.findNodeDataForKey("myKey");
theNode =   `$(go.Node "Horizontal", {location new go.Point(240, 80), key: "myKey"}
 etc. );

No, you should just call Model.addNodeData within a transaction and make sure that the data object that you add has all of the properties that you want and that the node template has all of the data bindings that you want.

I assume you have already read:
http://gojs.net/latest/learn/index.html
http://gojs.net/latest/intro/index.html
http://gojs.net/latest/intro/buildingObjects.html

Please read:
http://gojs.net/latest/intro/usingModels.html
http://gojs.net/latest/intro/dataBinding.html