How to add posts to Mailchimp?

I’m doing something wrong, but what?

I installed the Mailchimp for WP plugin. I opened an account with Mailchimp, set the api and my newsletter works. The only problem is that there no content in it. Just a bare newsletter. When I look for tutorials, I find lots of how to make a subscribe button, how to modify a newsletter layout, but nothing how to add content to that newsletter.

I’m using the Newspaper 7 theme. How do I add my posts to Mailchimp? The plugin I’m using doesn’t seem to do that. Mailchimp is entirely new to me, so any help will be greatly appreciated. I can make a manual newsletter, but that’s way too much work to do on a daily basis.