add bookmark on homescreen – where is in thesis 18 files

I have a customized theme built on thesis 18. I want to add a custom iPhone icon for the blog’s site when it is bookmarked on the user’s iphone/mobile homescreen. But in the thesis 18 there isn’t a header.php file where I would typically put this:

<link rel=”apple-touch-icon” type=”image/x-icon” href=”/images/dm-iphone-itouch.png” >

Anyone know where I can put this and have the same result?