The answer to that question depends on what you're doing. Do you want to enlarge what's printed or enlarge what you see on your screen? I have an answer for both!
BeadTool uses a templating system called Layouts for printing. Templates can be created and customized in many ways. BeadTool has some built-in Layouts for you to use, too. To learn more about layouts, please watch this video.
There are a couple of ways to do this depending on what your needs are. The obvious way is to click on the Zoom button on the toolbar.
Another way is to edit the actual pixel width/height of each bead in your Options. To do that just: