You can navigate to a charging station as your destination or set it as a waypoint the standard way, just like with any other place on the map.
Additionally, while Sygic is in EV mode it will always offer you the option to add a charging station to every route you are planning. On the route overview screen, just before you start navigating, an additional banner with the text “Customize charging along the route” is displayed. Tapping on it will show you icons on the map of all charging stations that are within a very short distance from the path of your route. You can select between them by tapping on their icons to view their detailed information and add one to your route.