This little thing is pretty flexible and will resize itself to fill whatever space you give it. You’ll want to enclose it inside a tag of some kind that has a fixed width applied to it. A table, div, span, or even p tag will work. If you don’t constrain this thing with a width, it becomes a monster and will fill the whole page. The example to the right is constrained inside a div tag that has a width set to 200 pixels.
John has built a nice page with further explanation of how to implement it. That page contains examples of the Syndibox, that’s my name for it, sized in different ways, along with the code necessary to include it on your page.
I’ll just add that if it’s a blog you are running, you can probably just drop the script right into your sidebar and it’ll resize itself to the width of your sidebar.