Adding theme app extensions to app

[ViktorasssIT]

Hi fellow developers!
I need some help developing theme app extensions.
I have installed shopify cli and pushed to my app shopify given demo theme-app-extension.
The demo extensions works fine, but I am trying to use this as boilerplate and make it work for the app i'm currently developing.
So the question is:
I can use metadata inside the liquid file (Example below)

How to prepopulate the data inside the schema, so that the user would see the data which is saved inside our app? As I understand, the user settings needs to be saved in metadata, but how to display this metadata inside the schema? (Example below)

Love to further discuss this topic with others and learn more!