how to make a json web api secure

I am trying to make an app with react-native that displays data from a excel database. So far I have converted the data from excel to JSON and created a JSON web api to access the data from a URL using myjson.com. It works great to retrieve and filter the data but my only worry is that the data is not secure at all. Anyone can see the JSON array if they type in the URL. I am definitely not going to stick with myjson.com to store my data. I am probably going to host it using some service. My concern is that even hosting the data myself, the website will not be secure. How can I add some sort of authentication security to the website so that only people that use my app can view the data?