How To Subscribe A New Member To SendInBlue

Hi

I use SendInBlue to handle all Gravity Form acknowledgements and to mail our weekly newsletter.

How can I modify the S2Member Join form, found on this page - https://sippclub.com/sipp/join/ - to subscribe someone to SendInBlue?

If it’s not possible, can a Gravity Form be used in place of the S2Member join form at the above link, for Gravity Forms has a SendInBlue plugin integration?

Thanks.

Brian Bennis