connecting DSL and network

Hi, I currently have dial up internet service. I will be getting a model for DSL from ATT. I have a laptop not networked at the moment and a desktop networked with a room that will have the laptop in it. All of these computers are on the first floor but the router to network them is in the basement. (it is not wireless) The phone line splits off from an old fashion box with wires and screws then to each computer. How and where do I attach the modem to have DSL on each computer without having to have all the computers on at the same time. I am not very computer savy. So I need very specific information. thanks in advance.