Inserting and modyfing a GRE image is done through this dialog where the result also can be instantly viewed.

Text on label
The text that should be on the GRE image is entered in this field. The "Edit..." button will bring up the String dialog from which a field could be added to the string.
Label style
The label style is selected from this list which contain various buttons and menus. By clicking the "Customize..." button the GRE styles dialog will be open from which modifications can be made to the styles.