Usally on a case and Mobo interaction, the case may have 2 usb ports, and a audio out jack for headphones or something. on the Mobo, it has a series of pins called headers, say a USB Header, and a Audio out header. So ussually on your case it should come with some wires that will allow you to be able to hook the up to those headers. the 2 usb ports have their own set of wires and the Audio jack has its own set of wires.
Here check out this link
For this pic the yellow base with the pins are the usb headers for 2 usb ports.
http://www.3dnews.ru/documents/5014/usb.jpg
in this pic shows the connecters from your comp case that plugs up to the headers.
http://www.dansdata.com/images/newbox/usbconns480.jpg
and sometimes it comes in this form, insted of usb connectors on the case it hooks up to a PCI based usb port or ports.
http://athena.tweakers.net/ext/i.dsp/1000149121.jpg