mail chimp form (popup) from promo box / button?

I’m trying to get a Mailchimp sign-up / subscribe form to popup when the user clicks on a button which is inline with some text like

“Subscribe to Newsletter” <BUTTON>

Best way I understand to do this is to use the mail chimp for wordpress plugin which creates a [shortcode] for the Mailchimp form. Now I can use that shortcode anywhere. What I can’t figure out is how to link a button to that shortcode.

For example, if I want to use the Promo box with a button option (since it already formats text inline with a button), how do I link the button to that [shortcode] for the mail chimp form? And can I get it to open in a popup on the same page?

For popups I’ve installed “Popup Maker” which in essence creates a CLASS that I can insert into anything which will make that popup. But, in the case of the promo box, I need to create a LINK to that button — but how do I use a shortcode there instead of a link?

Ideally, I want to create the

“Subscribe to Newsletter” <BUTTON>

In the footer so it’s on every page (but then it popups mailchimp’s form when the button is clicked, since it’s larger than just an “email” address slot — I have a few other things for users to fill out as well. How would I get this done?

Thanks.