Add new object to a list of objects

I have an object called Business that has a list of Object type “Order” in it. The order object has a field for name Business. The Order object has a field for type Business so that a Business can own a list of orders created. For some reason I cannot figure out how to make sure that when I create a new order and assign a Business to it, that it actually shows up in the Business List of Orders. I know it can be done but I must be missing something fundamental.

Hello. Would you mind sharing your data structure ( the data types tab)?