To re-install the app on iOS, you will need to delete the app from your device and then re-install it from the App Store. To delete the app, press and hold the app icon until it starts to wiggle. Then, tap the x in the top left corner of the app icon. You will be prompted to confirm the deletion. Once the app is deleted, you can re-install it from the App Store.
To re-install the app on Android, you will need to delete the app from your device and then re-install it from the Google Play Store. To delete the app, open the Settings app and navigate to Apps & notifications. Then, tap See all apps and select the app you want to delete. Tap Uninstall and then OK to confirm the deletion. Once the app is deleted, you can re-install it from the Google Play Store.