NOTE: Before you make a mailing list opt-in form block you must first add a Mailchimp API Key.
Creating a mailing list opt-in form block will allow you to embed a form for visitors to sign up to a Mailchimp mailing list.
In order to add a mailing list opt-in form block, click on the inserter icon.
You can also type /mailing-list and hit enter in a new paragraph block to add one quickly.
This is the Mailing List you want to add your visitors to.
If your audience has custom fields, you can choose which ones to include by checking the associated checkbox.