Actually, creating a Child Theme is well documented in the Codex along with lots of tutorials.
As for changes you make to the Customization screen in the parent theme, you’ll need to export those and then import them into your Child Theme. The Child Theme doesn’t inherit Customizations (I think). But there are Customization export/import plugins that will help with that. They will get all of the parent theme’s customizations into the private theme.
Not sure that you need any extra code in the Child functions.php file. All of that should be handled as the Child Theme is loaded. As I understand it, the Child theme is loaded first, then the Parent, so anything missing from the Child is loaded from the Parent.
(Also, not sure why the downvote. I’m not a big fan of downvotes. I figure any question asked here is important to the person asking the question, and deserves the politeness of a reply, even if it is to remind them [gently] of the proper questions to ask.)