I don't know what equipment your AT&T DSL came with. If you are just hooked up with a hard wired single computer I will guess that you will need a Router with Wi-Fi. I bought a NetGear one at Best Buy for $40 a year or so ago looks like they have dropped the price even more.
I've got 2 desktops hardwired to it and one wireless laptop all sharing files, and a printer across the network.
Also the wireless is encrypted with password protection so strangers don't get on the network.
The laptop I have now has built in Wi-Fi but if you don't have built in Wi-Fi one of these adapters will work.
The software firewall is all I use.