You just need to visit the App Store on your iPhone to download it again.
There are two ways to find the App in the App store. Open the App store icon and...
1 - Tap the search icon - bottom right, and search for iFootpath. Then just download the App.
2 - Tap your account icon - top right. Then tap 'Purchased' and you will find the App. To help you can tap 'Not on this iPhone'
You will then need your Username and Password to login.