First, make sure that the drive dip-switches are set appropriately; for instance, if it's IDE make sure that it's a slave. Then turn off the power, install the drive and turn the sucker on.
During system startup, the computer should automatically recognize the addition of new hardware, and will at-least configure it. It's quite possible that the computer will see it and mount it, because most drives these days come with a Windows (yuck!) FAT32 file system already installed. (But you probably do not want to use this filesystem-type with Linux.)
Red Hat probably includes a Disk Management tool which, through the GUI, will allow you to reformat the drive. Choose an ext3 filesystem type.
All in all, it is perfectly reasonable to plug the new drive in correctly and start 'er up and see just how far you get without doing anything special. Start there.