Take a look in your computer's task bar for an icon representing your wireless network. Look for a little computer icon with three green radio waves emitting from it; that's the Windows icon. Another version of the icon looks like four cascading horizontal bars, usually green; that's Dell's icon.
Double-click on the icon. In the case of the Windows icon --- the one with the green radio waves --- you'll see a dialog box marked "General." One of the tabs will be labeled "General." It's the default tab, so it should show immediately.
Look at the second line down under "Connection." It will indicate the name of the network or the SSID. The first line will be labeled "Status" and will be marked "Connected." The second line will be labeled "Network" and the text next to it is the name of the network, or the SSID.