Import/Export
Currently, only Helium-generated backup files (a JSON format) can be imported into Helium. However, you can add feeds for external calendars that are an ICAL format from the "Preferences" tab of "Settings".
You can also export a Helium schedule into an ICAL format (importable into most calendar programs). To do this, go to the "Feed" tab of "Settings" and clicking on the schedule you want to download.