If you reloaded from a Dell disk, it should have installed the driver but if you didn't or if it failed to, go into Dell's website for your country, find Laptops then Drivers and Downloads, input your Service tag (printed on a label underneath your laptop) and you can find all the right drivers for your specific equipment. Check the wireless adapter is the only one you need before you go there.
Drivers you download will be .exe files so when you transfer them over, the need only one double click to start the process.