Hey Andrea - I found some obstacles in using this application and was able to solve them. I thought you and others here would be interested in what I found.
Obstacles:
* If you have a personal page and a business page you can only get the optin box on the personal page
* The tab for the Profile HTML cannot be personalized to read what you want it to read e.g.; Newsletter
Solutions:
* I found an app called static FBML. You can find this in facebook search.
* This app allows you to add a "box" where you can put any html. Simply copy the code from the Profile HTML app into the FBML box and change the title on the tab - voila you have a customized box that you can display on your business page and your personal page is left for personal stuff!