Okay, i have a laptop with AT&T high speed internet. I have their modem but it is not wireless.?

I was wondering what do i need to have to get acces to wireless internet? Like sometimes i take my laptop to the living room and i connect to linksys but that work only sometimes and i dont even know how it happens but most of the time it doesnt connect to it. So i was wondering what would i have to buy to make my laptop be wireless and for me to be able to connect to the internet wirelessly any time i want? one more thing..my laptop has a wireless antenna which i dont know what it is but i tought i might help yall out....