[Gemma]

Create a new widget. Static HTML and give it a title/description.

Then configure it and place all the given code in the textbox and change the two instances of PAGEID, so it is something like this (I used Android as an example)

<link href="https://plus.google.com/104629412415657030658" rel="publisher" /><script type="text/javascript">
(function()
{var po = document.createElement("script"); po.type = "text/javascript"; po.async = true;po.src = "https://apis.google.com/js/plusone.js";
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(po, s);
})();</script>
<center> <g:plus href="https://plus.google.com/104629412415657030658" size="badge"></g:plus></center>

Then add the widget to your page layout.