Hello,
I am able to add an image to the menu, but i cant make it big as in the Demo, what am i missing?
Demo
http://alfredocardozo.com/wp-content/uploads/2013/01/demo.png
My site FrontEnd
http://alfredocardozo.com/wp-content/uploads/2013/01/mysite.png
My site Admin
http://alfredocardozo.com/wp-content/uploads/2013/01/admin.png
Please help me.
Create a new thread and tell me what problems you are encountering and what you want to know. 
There is no step 3 :) 
