My geocode API is not working

It is giving the following error when i try to print the content.
I have done exactly as shown in the video.

{
“error_message” : “You must use an API key to authenticate each request to Google Maps Platform APIs. For additional information, please refer to http://g.co/dev/maps-no-account”,
“results” : [],
“status” : “REQUEST_DENIED”
}