Enable the frost protection circuit if your system has one available. A sensor will detect when the temperature is dropping to where frost is a risk and will activate a heat pump that will warm the panels enough to where frost can't form.
Apply glycol to the panels in accordance with manufacturer instructions. Glycol can usually be applied with a soft brush. It works by lowering the freezing point of the panels so frost can't form under normal weather conditions. It is a main component in engine antifreeze for the same reason.
Cover the panels with a protective cover in the event of heavy snow. Some automated solar panel types open and close automatically.