adding a button to a template

[awkward_clam]

Hey all. I use a WP template and wondering how difficult it would be to add a little image button onto my site.  Not sure if this falls into PHP, JS, or CSS

 

Site in question:

http://www.lushwebsites.com

 

I want the button to the left of the little thumbnails in the middle of the page (divid= "featured-thumbs")

 

I know sometimes it's difficult customizing themes without messing sh** up, but if it's possible to add a little code and css so that there is just a nice little sign up button on the home page?

 

Cheers,

J

 

note: not sure which code to post, if someone will let me know.  thanks