File browser button in background

I already know how to use js callback to add logic nodes to a coded project.
So i am struggling to find a way to add a button for the viewer that will browse for pictures and it will be placed behind the object in the scene.
It will be of a determined size that i wd have to add to the code. How could i accomplish that? Where should i go to find this code snippet?
Can i just add to the .js code?

Thank you for any suggestions.

Use tag input with type=file https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/file