To build a mobile app with React Native: 1. Install Prerequisites: Install Node.js. Use npm to install the React Native CLI: npm install -g react-native-cli. Install Android Studio for Android development. 2. Create a New Project: Open your terminal, navigate to the desired directory, and create your project: react-native init MyApp. Navigate to your project folder: cd MyApp. 3. Run the App: Start the development server and launch the app on an emulator or connected device: react-native run-android. 4. Build the App: Write code using JavaScript and React Native in the android directory. Test on multiple devices for compatibility and performance. 5. Optimize and Publish: Improve performance by optimizing rendering, data fetching, and caching. Generate a signed APK and create a Google Play Developer account. Submit your app for approval on the Google Play Store.