Let's make steps:
1. Visit the Google APIs Console at https://console.developers.google.com/apis/library and log in with your Google Account.
2. Click on the Select project tab in the top menu.
3. Click button on popup Select project tab in the top menu.
4. Fill project name and Create. Wait a moment…
5. Check your notifications on top menu, click to view project.
6. On Dashboard click “Access the API overview.
7. Click on the Credentials tab in the left menu, the “API key” in the “Credentials” box to create Google Map API Key for browser apps.
8. After create API, the “API key” will show for you.
9. Click to API keys to edit, choose HTTP referrers (websites) and fill Your domain
10. Enable some APIs in Library tab
Last step: Get the key and paste it in the setting page.
Note: It can take up to five minutes to apply this setting.