Mailchimp API - how to pass apiKey to Mailchimp

Hi everybody,

i’m trying to use the Mailchimp API.

After got the API Key, I got the following instructions:

then I set up the api1 in my test page:

setting the api endpoint and in the header

user:

then clicking on fetch schema:

Schermata 2018-11-24 alle 12.55.40.png725×293 12.8 KB

I got the following error:

There is anyone who has experience with Mailchimp api and how to pass them the api key?

Thank you very much

Roberto