Sending Push Notifications is not a trivial thing but using Expo React Native app, it is quite straight forward. Here is a simple example to send Push Notifications using Expo React Native App.
You need to install expo-notifications package for send notifications. The expo-notifications provides an API to fetch push notification tokens and to present, schedule, receive and respond to notifications.
You can install expo-notifications by running following command:
expo install expo-notifications
Add this in your app.json android attribute:
And it will look like this:
Here is the Gist of App.js file:
And here is the GitHub link for this sample app Create and Send Expo Push Notifications. https://github.com/pimedia/Expo-Push-Notifications.