Google place ID is to uniquely identify a place in the Google Places database and on Google Maps.
How to get your Google place ID?
You can get your Google place ID by clicking here and then search for your address on the search bar. Soon after, it'll show the location on the map with a red marker and provide you your Google place ID.
How to add your Google place ID to your Floranext?
You can do so by going to Settings > Website settings > Social media. You'll see a field for "Google place ID" where you can add your place ID and don't forget to hit "Save" at the top right.