To use Google as a provider, you must get a key for a project via the API console. To do this, follow the guidelines on the page at https://developers.google.com/maps/documentation/geocoding/get-api-key. When you reach the limit--2,500 hits per day--you have to activate billing and expect to be billed.
The configuration keys to set in neo4j.conf are as follows:
apoc.spatial.geocode.google.throttle=10 #delay between queries to not overload servers and/or explode your billing, in msapoc.spatial.geocode.google.key=xxxx #API key for google geocode access, like AIzaSyCGOqPxaXkODpAKg_teles7tprisqu3icro3yaitpren7dre
I must underline that a third provider is supported by APOC, named OpenCage (https://geocoder.opencagedata.com/ ...