I just followed a tutorial about how to create a shopify app (https://www.youtube.com/watch?v=PIXN032XJJ8)
It's working, but I can't find a tutorial or documentation talking about how to add content to the store itself.
For example I want to add the sentence "Hello World" or simply a js script to each store where my app is installed.
What should I be looking for in the documentation ? Do you have any links ?