Demo based on - Build Mobile Apps With Flutter and Google Maps (Cloud Next '19)
You'll need to enable google maps services in a google cloud platform project and create an api key to access the services. After that, you'll have to insert your api key in 3 files inside the project (just serch for "api_key_here"). The files are:
You'll have to create a new firebase project and add apps for android and iOS. After that replace "google-services.json" (android) and "GoogleService-Info.plist" (iOS) files and replicate the database and data within Firebase's Cloud Firestore. Cloud Firestore is pretty straightforward and you won't have a hard time replicating the database shown in the demo on youtube, I guess :)
Just in case, here's a screenshot shot of my sample Firestore database:
I hope this helps!