Custom CSS for a Beginner

I am trying to customize my social share buttons on my home page. I would like them to be bigger, center, and go across the full width page. I have never dabbled in coding or custom css (I don’t know what CSS means…). Can anyone help me or tell me where to go to get help. The social share buttons on the homepage I want to be going across the bottom of the landing before the user scrolls. The look I want is a full width full screen background image with my logo in the center and medium sized round social share button going across the bottom. Once the user scrolls the social share buttons will move up along with the image and logo.

P.S. My vision is also to have (at least for the landing) matching navigation. I would love to have my full width round social buttons at the bottom and round buttons for my pages at the top. But that’s a pipe dream, I just thought I would throw it in here.

https://borderstoborders.com/