You do not need Seagate software, all you need to do is attach the drive, open Applications > Utilities > Disk Utility then select the new external drive and choose Partition.
I would set the drive up with two partitions, just divide it in half...1.5 TB for each partition.
Click on the first partition, give it a name, something catchy like Backups, then take the default Mac OS X Extended (Journaled) and GUID partition table options, then apply those to format the partition.
Do the same for the second partition but with a different name, of course, and when done, Quit Disk Utility.
Then go to System Preferences > Time Machine and turn it on, select the Backups partition as the destination, and let it do its thing. It will continue to work in the background periodically updating the backup with any new material you have.