Comp techs, about networking (2 comps. in same house) let me clarify, I have DSL kit 2701HG res csi gateway,?

from ATT, I have High speed internet on the phone line(No Voice Service) no telephone, Its new, maybe 2 mths ago, (10.00 mth. for no voice serv.) what do I need to get 2nd computer on internet, wireless adapter? or more? I know nothing about comps. Please put in detail, as I'm computer idiot!! Thanks,