1) start a landing page using Unbounce.com and reach out to some 1st degree connections to be testers
2) start gathering some data to validate your idea--talk to the people around you and ask them questions that revolves around this topic.
3) If it's a Web app, maybe start working on the mobile UI
4) Research competitors (I would check out Okcupid), partners, financial prospects, etc. Learn the industry and do you homework!
Hope this helps! Let me know how it goes!