Share Buttons are plugins that let your blog readers share your content.
Sharing buttons help you to increase your audience by engaging with people who are not on your site, as well as distribute content across multiple social networks and platforms helping to drive traffic to your site.
The one I use is SumoMe WordPress Plugin. After you install the plugin there are very easy to follow instructions to customize where you want to place the plugin.
The best place to put your share buttons is at the bottom of your content. This way you will be keeping the page tidy
and the user can share straight after they have read your content.