Here's how to use and apply new icons in just a few quick steps:
1 Download the icons
If you haven't already, download the icon pack above on your phone (or elsewhere), and save it to "Files" on your iPhone so you can access the folder from your device (or you can save it to "Photos" if you'd prefer)
2 Open the "Shortcuts" app and tap "+"
You'll be creating a "Shortcut" to your app, which will add a new icon for it on your homescreen that adds a new way to get to your app.
3 Tap "Add Action"
4 Tap "Scripting"
5 Tap "Open App"
6 Tap "Choose"
At this step, choose the app you'd like to create your new icon for.
7 Tap the "Share" icon at the bottom
8 Tap "Add to Home Screen"
9 Tap the "Icon" button
This will bring up a file picker for you to choose your new icon for the app. This might be in "Files" or "Photos", depending on where you've saved the icons in Step 1.
You'll also need to enter the name you'd like to appear for your app on the home screen (but you can leave this blank if you prefer a more minimal look).
10 Tap "Add", then "Next" at the top right
The new icon will now be on your homescreen, but there's just one more step to tidy things up!
11 Name your shortcut, tap "Done", and you're finished!
12 Repeat this process for each icon you'd like to add