Blog settings > widgets > Insert Free Html widget

Another way, if you're feeling adventurous and have a wee bit of comfort with "php and html mixed together", would be to edit the correct file in your /skins/yourskin/ folder and just put the html right where you want it. Technically I'd guess that is going to be easier on your server than a Free HTML widget, but it takes more work to get it done. Free HTML widget is cool cuz it is really really easy :)