Hi Johannes
It will work, as it is MAC OS compatible.
The 4 inputs will show up in Garageband, according you open the same number of tracks and assign each of them to one input. You will most likely find the information on how to connect your audio interface to your computer (USB or FireWire), and then you read Garageband user Manual 🙂
Just my 2 cents, I wouldn't suggest Behringer. Their high-end product may be defendable, but the lower end like this podcast station aren't always good for the sound recording. Depending of your use of the product and how professional your work has to be, you might want to consider other setups. I say that because I used to own a Behringer Mixer and it sounded like crap, not to mention all the noise. But again, the best is to go to a music store and try different ones... You're the one who will use it.
Have fun!