For your website to use Google Maps, you need to have an API key. The API key is a unique identifier that is used to authenticate the requests from your website, and to return Google Maps on relevant pages.
You will need a Google Account before your start.
Firstly, to get the API key, you can follow Google's instructions here.
Then to add it to the Homeflow CMS, click on the "Site Appearance" link in the left hand menu, and choose the "Config" tab on that page. One of the boxes is for "API keys", and you copy the Google Maps API key into the box.
Once you click "Save site" at the bottom, the API key is stored.