In your app store or google play store you will want to search the app you are looking to update.
Coach App - Coach Catalyst
Client App - MyCoach
Branded App - the name of your branded app
Below you will see what it looks like when you search Coach Catalyst on an iPhone. Where it shows OPEN, it would say UPDATE if an update is available. When you search Coach Catalyst, below it you will see MyCoach which is the client-facing app. You can have your client search MyCoach to update their app.