Mailchimp: Do I have to add MP custom code to make connection work?

Hi! I checked the video “How to connect WF with Mailchimp” of course, and I know how to add the action URL to the form, and all of that – but my form still doesn’t work. I found a tutorial, and someone describes that you have to go to Integrations in MP, and under Custom Website you have to enter the URL of your site, then MP generates some code that you’re supposed to add to custom code in the site settings, and then you should check in MP if the connection is running. Could that be necessary to make it work? I never heard of that before. –Frank

Here is my site Read-Only: LINK
(how to share your site Read-Only link)