How to configure linksys wrt 54g router in apt building w/ethernet jac

i'm in an apt building at school that gives you internet in each room via an ethernet jack. When i plug xbox 360 or my mac into it directly it works without a problem. Then i plug my router in to make my apt wireless and it doesnt seem to let the signal through and send it out. IDK what settings i have to change or what. i have renamed the router, changed the channel and added a password. any help would be appreciated.