If you click the Connect to CoA button in the secondary actions menu on in a Cargo Drawer,
you will open the Connect to CoA modal:
In this modal you choose which CoA Line you want to connect the Cargo to and click Confirm to connect it. Doing so will update the Company and Business Unit of the Cargo to be the same as the Company and Business Unit of the CoA.
When you have connected the cargo to a CoA Line, you will see a chip at the top of the Cargo Drawer that says Contract of Affreightment as well as which CoA Line you've connected it to (40129002 in this example).
The CoA number chip (40129002) is a clickable chip that will open up the drawer of the CoA.