You can manually place the the following code anywhere, in the Page or Post content as well as in a Text widget in the sidebar:
<div id="share"><div data-layout="button_count" class="fb-like"></div><a href="//twitter.com/share" class="twitter-share-button">Tweet</a><div data-size="medium" class="g-plusone"></div></div>
If you need more advanced support, we recommend this plugin: