Need to grab an element in a submit form but can't?

Site: http://www.studio3creative.co.uk/edsi/

Hi, i am adding a plugin to my site which allows the submit form to connect to a 'dotmailer' account. I have styled the horrible form it came with to match the site but i cant get hold of and style the 'submit' button at the bottom. could you see if you can and send me the css to grab this element so i can alter its width font and colour and increase the nargin above it.

Here is a screengrab to show you the element.

https://www.dropbox.com/s/3polvvtn6jsv42u/visual.jpg

Many thanks in advance.