circle icon widget and pictures

I’m from Argentina so I hope you understand me.

I am creating my webpage with wordpress and using Vantage theme. I have just added a circle icon widget and it gives me the possibility of putting it on the header, on the footer or on the siidebar. My problem is that I want to put it in none of them. I want it on the center, just as it was in the preview.
There is a link attached for you to know how I want to put it.
Also I wanted to know how to change the pictures of the gallery which is under de header. (The gallery that says “Integrated with some fine plugins”here