From MailChimp Dashboard, go to Achieve.
Click View Contacts.
Upon selecting View Contact, you’ll be redirected to the Audience page at Manage Contacts tab. From here, switch to Signup Forms tab.
Then select Embedded Forms.
On the Embedded forms page, at the Classic tab, find the Copy/paste onto your site module and get the Action URL as shown in the photo.
Done! You are all set.