You can just go to http://www.factual.com/contact and type your info to the right of the prompts in the “Your Message” box.
I don’t believe the “Factual ID” field is required unless you’re editing a listing that’s already in the system but incorrect.
As I wrote before, Factual makes it easy for you to list your business. They seem to take maybe two-thirds of my clients’ submissions on the first try, so sometimes you need to keep working on your supporting citations and try again later. Other than that, it’s a pain-free process.
They’re making it real easy for you now. Go forth and list yourself on Factual. It’s free, and important.