Each skin contains custom icons. Here's is video guide how to install them:

Detailed Guide

1. Launch Shortcuts app:

2. Create new shortcut:

3. Select Add Action:

4. Select Scripting:

5. Select Open App:

6. Select desired app:

7. Click More button (three dots):

8. Type app name:

9. Click Add to Home Screen:

10. Enter desired name:

11. Tap on the app icon:

12. Tap on Choose File:

13. Locate On My iPhone folder:

14. Open Themes folder:

15. Open Theme folder:

16. Select app icon:

17. Tap Add:

18. Done!