How do you activate Google Maps JavaScript API v3 service?

The tutorial doesn't say how to activate the Javascript API v3 service. It just says do it. My Google Developers Console screen doesn't match the screen they show in the written (probably out of date) tutorial.

There is no "Service" category for me to choose. I have a "Terms of service" category which, when chosen, allows me to read the terms for this particular API but there is no action to be taken in that window. I have an API key and I have entered the code in my web page and placed my API key in it.

I get the following error message when loading the web page: "This page was unable to display a Google Maps element. The provided Google API key is invalid or this site is not authorized to use it. Error Code: InvalidKeyOrUnauthorizedURLMapError" and I think it may be because I have not been able to "activate" API v3 for this project.

I have tried the following:

Regenerating a key and using it immediately so I know it isn't that the key is over 24 hours old
Double checked my referrals
Accurately entered the name of the site where I am trying to make this work.

How do I activate maps API?

Go to the Google Maps Platform > Credentials page. On the Credentials page, click Create credentials > API key. The API key created dialog displays your newly created API key. Click Close.

Is the Google Maps JavaScript API free?

The Maps JavaScript API uses a pay-as-you-go pricing model. Maps JavaScript API requests generate calls to two different SKUs depending on the type of request: map loads or panoramas. JavaScript services are priced separately from JavaScript native SKUs.

You need to activate API from the Developer Console

reach the maps api v3 on google cloud console