setting up airport extreme to earthlink dsl modem

Hello,

I recently bought airport extreme, the old version (and used), for the purpose of using it as a router for my zyxel p-660R-d1 dsl modem.

I am not at all good with computers, let along setting up an internet connection, so I am very lost and need help.

So, I just switched my service from Time Warner to Earthlink, because I only need internet connection, whereas previously I was bundled with TV and home phone. Earthlink sent me the modem, and self start-up guild and whatnot. And I realized that I don't have my old router with me, and decided to buy a new one, because I have already purchased my earthlink plan without the company provided router.

I read though reviews, and figured that my 802.11n wi-fi wireless Base Station would do more than enough job to make wi-fi connection throughout my apartment suit.

As I was trying to set up my router with the modem, I read the instruction for starting up guide with airport extreme. From there

it seems to tell me that I need a device called AirPort of AirPort Extreme Card?

I am a little dumbfounded and not wanting to believe my situation, because I thought Airport extreme as just like any other routers I have purchased that just worked by it self.

Am I reading into this wrong, or do I really need to buy additional things to get my internet connection up and running?

If I indeed need something else to get this thing started, can you please give me exactly what model to buy so that I don't end up getting in a trouble

like i just did to myself? If there is such a thing as different versions for AirPort that is.