When Modeler is loaded the objects and models become available in the Labeler Dialog. If you have the labeler open before loading Modeler you may have to refresh the dialog to see the added options. You can refresh it by selecting any of the other tabs and then returning to the first tab, or you can restart labeler.
To label spot elevation from your modeler project, select the object or model you want to draw your elevations from. If you want to include stations and offsets from an alignment in your labels, select the GPK project and the alignment in the setting. Once these options are set and you select a point or element, you will see their corresponding values are applied to the label components when you pick one in the list. Then it is just a matter of picking and adding them to the label.