iContact Plugin – how to stylize beyond basic css

I would like to use the function of iContact but style it more like a button and use it in the header. This is a perfect example of my end-goal: http://kyrstensinema.com/

I have the iContact plugin and can set it up in a widget no problem, and I can adjust the CSS to do simple changes like remove the borders, change the font color, but I’m not sure how to make the jump to the example in the link above, such as styling the submit button or having “Email Address” appear in gray in the button rather than having it written in front of it.

Any guidance or tutorials would be greatly appreciated. Thanks!