Mailer lite form show on click event

Hey there,

I wanted to add the newsletter form that opens a pop up if you click on a link or button, that Mailer lite offers.

Mailer lite gives me this code (after I inserted the JavaScript):
<button class="ml-onclick-form" onclick="ml('show', 'QWgyyH', true)">Click here to show form</button>

If I insert this in an inline text or html shortcode inside the tagDiv Composer it will show a simple not styled button (that works great when I click on it).

My question is, is there a way to style this (I suppose) default WordPress button?

Or, even better, to use this code in some way with the button shortcode in the tagDiv Composer, to style the button and make it look like a Call To Action button?

Thank you!
Dominik