How do I add my business to Apple Maps?

That is poorly documented. I would start here:

https://register.apple.com/placesonmaps/

If that does not help then you need to contact Apple Support. These forums are user-to-user venues and Apple won't respond to that type of question here.

Go to this page, type in the name or address of the place that you want to add, and then follow the instructions to claim it.