Add a WP User when adding to Mailchimp List

Hi, a Newbie question.

What I need to do is this: I have a subscription form to my Mailchimp list which works just fine. A new user can enter their details and Mailchimp does its thing.

Now, when they have registered with MC, I want them to automatically be a Level 0 user on my WP installation. Is this part of what is supposed to work or am I barking up the wrong tree?

If this doesn’t work, how on earth do I set this functionality up?

Thanks in advance.

PS> I have set up MC API Key and List ID in s2member

https://ww.wp.xz.cn/plugins/s2member/