How to connect xbox using wired connection?

my modem is different than ones i have seen before... its a modem but its wireless, no router needed. i have got an xbox and its my friend's. somehow i cannot connect to xbox live using wireless. he mentioned something about not having wireless equipment ( i am not sure what) so he asked me to do wired instead... okey so here is what i have been doing.. i connected my modem with my xbox using line jack. but when i try to sign in it says.. no internet connection detected... i dont know wahts going on.. plz help.. fast. pzl plz plz