Customize a Third Party App

I'm looking to customize the look of an app once it is downloaded from the app store. My barbershop's app is running on an app called "mybarberapp". Our clients download this app, and plug in a barbershop code so that the app can access our information. But when they exit the app and return to it in the mobile device, it shows the generic app image and the app name as "mybarberapp" and does not represent our company. I would like a solution to this. My goal is to have our image and name "House of Barons" in peoples phones with the internal fuctionality of the "mybarberapp".