I installed a d-link router. Now I'm being asked for a key to log onto my wireless network. What key?

I installed the router and thought I followed the disk directions to the letter. I was asked to choose a SSID. Did that. Finished up the installation process and when I went to log on was asked for a security key. I'm glad of that. Keeps the vermin off (LOL). Problem is, I don't have a clue where the security key comes from. Did I, in fact miss choosing my own key or is it program generated? HELP!!!