Form submission and Marketing Tick Box

Hi everyone, 

I have a "book a collection" form on my website. In this form, there is a tick box "stay in touch" for my marketing mailing list. 

This tick box was linked to our Mailchimp account, as we used to do our newsletter there. We recently stopped using it and started doing our Marketing on Squarespace directly. However, the email addresses of the people who tick this box are still going to Mailchimp, and I have to manually add them to Squarespace. 

I went on the form, and in "additional storage" I can disconnect from MailChimp. But in the connection options there only are "Zipper, google drive or mailchimp". 

I am looking for a way to have these email addresses sent directly to my Squarespace mailing list, but can't seem to connect it. I have tried to just disconnect Mailchimp, thinking maybe the default was Squarespace, but as a result, if I fill out the form, the email address isn't shared anywhere at all. 

Please help? 🙏

Thanks a lot, 

Manon