You should get Google API key.
Google provided Guide to get API key here: https://developers.google.com/maps/documentation/android-api/signup
My details and guide below:
My guide with screenshots: Link to download PDF
From time to time google change developer web interface but process should be very similar. Guide is available here:
On YouTube you can also find this process from other guys, os, systems. Just search for it, example:
https://www.youtube.com/results?search_query=google+android+api+key