I just had DSL through AT&T installed. I want to know how to connect my laptop to the internet.
Any advice will help me, thanks!

If AT&T left you with a modem, for a multi-computer home network, you would procure a router, possibly wireless, and then connect the laptop wired or wirelessly to the router. You may need a network adapter installed in the laptop if it doesn't have one built-in, most do. You can also connect the laptop directly to the modem with the correct cable and configuration if that's all that's desired.

If AT&T left you with a combination modem/router device, you connect the laptop to it wired or wirelessly as above.

Lastly, you configure the router and computer with TCP/IP addressing information so that they can communicate on the same TCP/IP network.

Did you get any documentation, CDs, or cables with the DSL? Most providers include quick setup kits to assist with configuring any included hardware and connecting one computer. Some will even preconfigure the included hardware in an attempt to makes things simple. Without specific hardware model information as to your setup or desired network, no one here will be able to provide anything but highly generalized installation info.