Welcome to the forum
As coolcolors said, we need more info - what model Dell do you have? Desktop or laptop?
If the drive is USB, your Dell should pick it right up, I have 2 external DVD drives hooked up to my own Dell desktop just fine.
Is there power going to the DVD drive? Does it eject?
Have you looked in Windows Device Manager to see if there are any yellow exclamation marks?
Guessing you're using Windows, of course.