Include the JavaScript SDK on your page once, ideally right after the opening <body> tag.
<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_GB/all.js#xfbml=1";
fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));</script>
Place the code for your plugin wherever you want the plugin to appear on your page.
<div class="fb-like-box" data-href="http://www.facebook.com/pages/Watterson-Marketing-Communications/123730957653138" data-width="280" data-height="395" data-show-faces="false" data-stream="true" data-header="false"></div>