Oh, ok. That's a little nasty on the part of Razer (a surprise to me), but no problem. You need an adapter that takes the one 3.5mm jack on your headphones, which carries the signals for both the microphone and headphones (microphone to the computer and headphone signal from the computer, of course), and splits it into two separate plugs. One of these carries the signal from the microphone, and the other carries the signal to the headphones.
Combined mic/phone plug (note the three bands, separating the regions for ground, right, left and mono microphone): http://img.alibaba.com/wsphoto/v0/506689242/3-5mm-Stereo-Headphone-Earphone-with-Mic-for-Samsung-Galaxy-S-i9000-S8500-Wave-EAR-136.jpg
Simple stereo plug (two bands, separating, ground, right and left): http://rocky.digikey.com/weblib/CUI%20Inc/Web%20Photo/SP-3501.jpg
What's nasty is that Razer didn't include the required splitter. I believe most gaming headsets either come with a splitter or simply have one built in: their wires split without any extra parts.
tl;dr: This is the adapter you need. http://www.dhgate.com/3-5mm-mic-stereo-audio-y-splitter-1-female/p-ff8080812c1cb652012c2ea9ba05676d.html