How to connect the internet Using linksys wireless router?

Hi, I have the network/internet connection using The AZTECH DSL600EU Modem/routerwith DHCP enabled. Now I have one Linksys Wireless router. I want to connect this Linksys wireless router to the AZTECH DSL600EU Modem/router. When I connect and giving the username & pwd given by the ISP I can't connect. Can somebody help me ?