Facebook ID code – where to add it????

Hi everybody
In my blog I have “Like” buttons placed below each image in my post pages; since I’d like to “see” who liked my images I found a tutorial on FB forum that explains how to do that.
This is how it should be done:

“Third step. Add the following meta tag between the head tags on your website. Please note that depending on what software or host you use, finding these tags could vary.”

The code I should insert is this:
<meta property="fb:admins" content="YOUR_ID" />
but I don’t understand where exactly I should place it.
thanks
Fabio