Okay, it was trying to surface attach, so I used the ALT key and it did attach. But now, when testing it, there is no decouple option when right-clicking on the ports.
CRAFT FILE: https://mega.nz/#!FQxgUKgL!sVqKOj8w48vXuNPqTUZPrSvWjSeWxfF-D7g5gKU6uiM
If anyone would mind looking at it, and explaining what I did wrong, I will be very grateful.
EDIT:
Got it to work - thing was, when holding the ALT Key to attach it to the port, it attached 'too deep' to the port. So, I had to pull it a bit back with the mouse while still holding the ALT key.