Just plug it into your Mac. Magic -- it works!
If you intend on using the drive solely with Macintosh computers and do not need to access the drive locally (via USB, etc.) with a Windows computer, I would highly recommend reformatting the drive to HFS+ format (a more Mac-friendly disk format). You can do this via "Disk Utility", located in Applications > Utilities.
What do you mean it might not be seagate? they sell the same exact model for $60 dollars more and say that one is mac compatible, but this one is not?
Seagate was trying to impose a Mac-Tax.
This stunt alone will insure I never buy a Seagate external. For any reason. Ever.
Way to go Seagate...