USB device developmet using NIOS II and Altera USB Core

OK, so I really want to know this. I can see that USB core exists for the Altera FPGAs, I think that Nios II or a HPS would be needed to be used with this USB controller core. I cannot find any documentation on how a USB device is to be developed using the USB controller and a Nios II. Any documentation or simple example will provide an immense help. Can any one provie help on this?