How do you promote your products？ please let me know，tks.

My andorid app GpsTestTool (GnssViewer) lasted 3 months and has been developed by myself. The main functions are as follows: 1.Number of GPS satellites 2.Satellite signal strength 3. Your current speed, heading and altitude are shown as text 4. Show your GPS coordinates 5. Compass function 6. The time in your current time zone 7. And UTC time, etc. 8. View the output of NMEA data 9.Save NMEA satellite data The GpsTestTool(GnssViewer) is quite powerful, the most important thing is that there is no in-app purchase and it is completely free. But I don't know how to promote my app. At present, there are very few downloads and very few users. what should i do?