There are two kinds of labels that appear on a node:
Node labels These are the labels in the center of the node. They appear when you are on a zoom level greater than 3 (there are 6 zoom levels total).
You can change the text that appears on the node by selecting a property from the dropdown under NODE LABEL:
Mouseover Node labels These labels appear when you mouseover over a node. They appear at all zoom levels.
You change the text that appears upon mouseover by selecting a property from the dropdown under MOUSEOVER NODE LABEL:
The label of a group entity that appears on the map is taken from the Name
attribute of the entity. Currently, there is no way to customize the property for this label, but it is on our feature roadmap.