Comment on WordPress Social Network Theme by Mark.

WordPress Promotion Theme Where can I adjust the size of social networking buttons that are at the top or bottom of the posts.? I tried CSS, did not see how these are created, maybe they are images, if so which folder?
I would like to significantly expand the size of these social buttons(or a custom image), yet keep it mobile responsive and not too heavy.
The objective is to increase shares.
Now days any social signal from shares to mentions help rankings and if the button is bigger or unique, I think it will help. I could draw my own image.