Cant connect to the internet with wireless ro

Hello,
im having troubles connecting to the internet with the belkin wireless g router with the att dsl modem.i connected all the cords right but still no connection.when i used the belkin installation disk, all the settings worked but when i got to step six,the router didnt connect to the internet.i was required to put my service name and it was all correct but still no connection.when i looked at the modem,the internet light did not appear.the modem model is siemens speedstream 4100.if anyone has a solution,please comment.thankyou.