need help i have a sb5101 w/haxoware 39 just purchased and i cant get online

[okojo]

ok plugged up modem changed my dns setting using several of the known dns setting out there... all of my light are synced but i still cant get online when i chose auto... dns i get the comcast page when i put in the dns settings ie...4.2.2.2 i get nothing i feel like i missed a step was there something else i was suppose to do when i got this modem please help i saw a few tutorial about logging in the modem but i didnt see where i needed to change anything or upload a file of some type... Is this what im missing am i suippose to upload something or change a setting? im on comcast in wash dc