Once you have downloaded the content you can take each icon and use the shortcut app to add the image to a shortcut you create.
- Go to the "Shortcuts" application on your phone
- Click "+" in the top right corner
- Click "Add Action"
- Search for then select "Open App"
- Click "Choose," then select the application for which you want to change the icon
- Click "..." in the top right corner
- Click "Add to Home Screen"
- Under "HOME SCREEN NAME AND ICON", change "New Shortcut" to the name of your selected application
- Under "HOME SCREEN NAME AND ICON", click on the icon and select "Choose File"
- Find your downloaded icon pack inside a folder in "Browse" → "On My iPhone" → "Zedge"
- Select the folder with your downloaded icon pack
- Choose the icon you want for the application
- Click "Add" in the top right corner and you should see a confirmation message that it has been added to your homescreen
- Click "Done" in the top right corner
- Exit "Shortcuts" app and you should see a new app with your selected icon on your homescreen (you may need to swipe to find the screen to which it was added)
- Your original icon for the application will remain, but you can move it into a folder and use your newly created icon
- Repeat with any application!