Login to MailChimp. Create a new list. Then, click on Lists on header menu. In the opening page, click on the bottom arrow next to Stats and click on Signup Forms. Then, click Embedded Forms.

You’ll see some HTML codes in Copy/paste onto your site.

Search for the code starting with <form:

<form action="//USERNAME.SERVER.list-manage.com/subscribe/post?u=USER_ID&id=LIST_ID" 

I wrote field names to be copied to Olympus wp-admin options as capitalized.