Centering the buttons under the post

I am attempting to center the block of share buttons under my posts, using the css style in the settings but can’t get it to do what I want.

I can set the margin-right and it shifts over nicely. But “margin-right:auto;margin-left:auto;” doesn’t appear to do anything on my post.

Here’s the page http://mattmckeephoto.com/2014/gilgamesh-indy-movie-poster-photoshoot/

https://wordpress.org/plugins/hupso-share-buttons-for-twitter-facebook-google/