If you would like to use the Google Autocomplete for your delivery addresses you will need to set up a Google API Key. Depending on your usage Google may charge for the use.
Go to:
https://console.developers.google.com/apis
1) Create a new project

Enter the Project Name and click Create
2) Click credentials in the side menu

3) Then click create credentials

4) And choose API Key

5) Click Restrict key

Choose https referrers
Then enter the domain name in the restricted domain:
*.yourdomainname.com/*
Click done

Choose dont restrict the key
Then click Save
6) Click Library in the side menu

Search for Places API and enable
Search for Maps JavaScript API and enable
7) Wait ten minutes

Copy your API Key, then go to Settings > Advanced Settings > Advanced Settings in your store and paste it into the Google API Key field. Update the settings to save.
Go to your website, add a product to the cart, and go to checkout to check that address autocomplete is working. This should happen instantly once you`ve saved the key.
If it`s not working, double check your settings are saved correctly. You may need to set up a Google billing account for the API key to be active.