I have a question regarding the Marketing Cloud App development for Appexchange.

When I create a installed package in the marketing cloud org, I get Api key and client secret with the help of which I can get the the Access token to make the API callouts.

But when someone install this app from Appexchange then how will the provider of the app(ie, me) will get the api keys to get the access token for making the Api calls to all the marketing cloud org (which will have different keys).