First, download and install it in the app store again.
Second, take iPhone7 as an example to restore the factory settings of mobile phones. The specific method is as follows:
1. First click the "Settings" icon on the phone desktop.
2. Then select the "General" option in the phone setting interface.
3. Then open the "Restore" entrance, as shown in the figure.
4. Finally, click "Restore all settings" in the restore interface, as shown in the following figure.