How to break into making software for businesses?

Hey so if I'm a startup with a few great coders working together to make a business-internal communication platform for budding businesses, how can I market my software? Door-to-door? Just some general notions would be helpful. I recently realized that a project I've had in mind for years would be a great fit for companies to communicate internally in a nice way via computer/mobile/screen.

Thanks, feel free to ask questions of clarification. Your expertise and attention are appreciated.