Write something to it? Seriously, the question is a little to vague. It should ideally show up as a new drive letter on your machine, which you can use like any other drive. Do you intend to back up to it, or what are you going to do with it? What do you want it to "start" doing?
If it does not show up as a drive letter, we can look at other things to see if it is detected at all by the OS.