The popup blocker may block the next step - you may hear a beep.
Various properties of the label may be set in the popup just below labeled axis label props... .
Click on the Jmol text in the above diagram to show a popup menu.
Click on the Source selector icon to open the Data Source selector icon to open the Data Source Selector popup window.
Be wary of sites that are mostly advertising or that put a lot of popup windows on your computer.