There's no special preparation, though, if you wish, could use something like gparted to partition and format the drive.
All you need to do is download the *.iso for Mint, create the installation media (either CD or USB), then start the install. When it asks you where to install the software, point the Mint installer at that hard drive and let it create and format the partition(s) to receive the install.
Linux Voice has posted a video of the Mint installer; it might help. It's the second one on at this link