How can i change the style of this text and button?

On my website, I am using this plugin: https://wordpress.org/plugins/mail-subscribe-list/ to create a widget that allows users to subscribe via email. You can see the plugin in action here: http://www.merchvintage.com/?post_type=product (on the top right under the header where it says “Never miss a new item! Get notifications via email whenever new merch is dropped”
I want to know how to change this text to match the other text on my website as well as change the style and color of the button that says”Submit” to match my other buttons.
The theme i am using is called ultra: https://wordpress.org/themes/ultra/