This will open a new page where you tap on "Open App" again

This will open a modal will all your apps

Tap on Search and start typing the app you want to add

This will open a new page where you can add your custom icon and custom name

Tap on "Choose Photo" or "Choose File" depends on where you saved your icons after you downloaded them

Pick the icon you want. (in this example I am choosing the instagram icon)

Tap on the name and change it to whatever you want. You can also leave it blank if you want to.

Now just tap on "Add" and you are done :)

Minimal Icons / How to use them

Minimal Icons Tutorial