No disc drive- how do I install?

I'm sure that this is a dumb question, but I've had my macbook for a few months and I love it. I need to install a disc for SPSS (a stats program). In the past I've been using windows so no problem, I've just loaded the disc and off i went. Can someone please explain to me how I do it now? I've obviously not caught up with new technology yet!!There is a Mac disc in there but obviously I have no disc drive now. Thanks so much