For iOS:
Press and hold the app icon on your screen for a few seconds until the icon starts moving and an x appears in the corner. Now tap the x and confirm the dialog. This permanently deletes the app from your iOS device

For Android: (varies depending on the device)
Press and hold the app icon on your screen for a few seconds until a trash can icon appears at the top or bottom of the screen. Hold the app icon, drag it on top of the trash can and let go. Now confirm that you want to delete the app.

There is another possibility to delete an app from your device. Open the settings and choose the app menu. Select the app you want to delete to open the app info. Now choose the deinstall option and, if necessary, confirm the dialog. This permanently deletes the app from your Android device.