The best way I'd recommend to add all the social buttons to a position is to use the JFBCSocialShare module. With that module, you can easily setup how each of the social network sharing buttons we support should show. When configuring the module, set it to a custom position, like 'center_article'. This is not meant to be a position that already exists in your template.
Then, use the loadposition plugin, which lets you insert a module into your content, like:
{loadposition center_article}
With that, you can easily change the settings for the sharing buttons and have it apply to all instances of your sharing buttons. It also gives you the flexibility to add the sharing buttons wherever you want in each article.
Alternatively, you could set the JFBCSocialShare module into an existing template position if it's always going to be in a fixed location.
I hope that helps, but if you need anything else, please let us know,
Alex