iMac and headphones with mic?

Quick question for you guys.

I have these headphones with built in mic that I'm trying to use for my Skype phone calls. I noticed I only have the 1 plugin on my iMac for input and output, how would i go about hooking it up. The headphones came with a USB plugin where you plug both the headphone and mic into and then you can use USB but i cant seem to find drivers for OSX. These are the headphones I'm talking about

Steel Series 5HV2

Any help would be appreciated. Thanks.