You just use the dot operator - the same as you do in vb.
Take this sample for example:
var excelApp=null, excelFile=null, excelSheet=null;
excelApp = new ActiveXObject("Excel.Application");
excelFile = excelApp.Workbooks.Open(filename);
excelSheet = excelApp.Worksheets('Sheet1');
As for methods/properties - they're quite simply what their names imply - properties hold information about the object, methods are things that the object can do (functions).
WorkBooks is a property, Open is a method of that property.
Worksheets is another property of excelApp.
Properties can be simple types, like int, char, byte etc - or they can be objects with several properties/methods.
But in short - property=data, method=function. :)