If you're asking about how to *start* spreading the word, my fear for you is that you haven't done sufficient customer development to validate the need for your app and inform your core product thesis. Failure to do so will almost always end-up in product failure.

If this is the case, you might want to slow down on your product building process and refocus on customer development. Building and launching a mobile app that achieves critical mass is one of the hardest challenges one can take-on.

Happy to talk to you in a brief call to outline the customer development process.