That's a hard drive, right? Not a flash drive? You should be able to format it no problem... in fact it should have given you a choice when you plugged it in. I'm assuming you have tried and that's what it said, not that you looked on the box. If you haven't tried it, do so.
If it's formatted for Windows and you can't get it to format, you can always install software to let your write to NTFS drives (by default, you can only read them).