Here’s some ideas:

-Start a blog and use content marketing to tell people about your app
-Submit your app to curated platforms, like Product Hunt
-Get local publicity and build a connection with influencers in your field
-Create an onboarding campaign for new app users
-Optimize the keywords of your app with App Store Optimization
-Focus first on getting 1 user, then 10, then 1000, then 10.000 -don’t try to make an impact on thousands of people from the start
-Use the network effect to build a product that gets better when more people use it, and help people share your app with others
-Set up an App Install campaign on Facebook, or use Search Ads in the App Store
-Use SKStoreReviewController to ask app users for a review (which subsequently boosts your App Store ranking)
Improve your app meta data and screenshots, and tell people about the benefits of using your app (instead of just listing features)