I answered this in the Templates, Stylesheets, Page Layout forum (it should have shown up if you'd searched 'Facebook'), but I'll answer it here again.
On includes/templates/YOUR_TEMPLATE/common/tpl_main_page.php copy and paste the following and insert it directly after the <body> tag.
Code:
<div id="fb-root"></div>
<script>(function(d, s, id) {
var js, fjs = d.getElementsByTagName(s)[0];
if (d.getElementById(id)) return;
js = d.createElement(s); js.id = id;
js.src = "//connect.facebook.net/en_US/all.js#xfbml=1";
fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));</script>
Place the code for your plugin wherever you want the Like button to appear on your page.
Code:
<div class="fb-like" data-href="YOUR URL" data-width="450" data-layout="standard" data-action="like" data-show-faces="false" data-share="true"></div>
That code gives you a Like and Share button plus how many people 'like' it.
There are other codes you can get from Facebook Like Button to do what you want. I use individual links on my product pages so people can Share and Recommend specific products on their Facebook. It's a little more involved, but worth it for me.
I don't use the Like button at all because Like doesn't get me free advertising of my products on Facebook, it's basically just a counter