Moving to a WiFi-only area with a Mac Pro?

I'm moving to a new city to go to college, and the only internet available in the apartment I'm going to live in is WiFi. I'm taking my Mac Pro (the tower, not the laptop version) with me, but it isn't WiFi ready. I know you get one with the card pre-installed when you choose your specs, but I didn't bother, since I don't currently live in a place where I would need one. I looked on Apple's web site and found an Airport Express, but that seems like something you need in order to set up a WiFi network as opposed to something you need to get your computer to hook up to a preexisting network. What do I need in order to access my new apartment's WiFi?