[Plugin: WP Email Capture] Edit the Widget?

First of all- AWESOME PLUGIN!

Secondly, I do see the “Other Notes” section here but just have a question about exactly what do I click on in the editor (e.g. wp-email-capture/wp-email-capture.php, wp-email-capture/inc/core.php) to do apply the edits to make it look like the demo? Thanks!

Link to widget page (in the footer):
http://www.coastalrealtorpros.com/

http://wordpress.org/extend/plugins/wp-email-capture/