I'm guessing the 2nd 500GB is the drive you're wanting to use? It currently is device sdb, located at /dev/sdb. It looks like it currently does not have any partitions, so we will have to create a partition and then format it.
To create a partition run this command:
This will launch fdisk modifying only drive sdb. When in fdisk, first you will want to use the letter "n" to create a new partition. It will prompt a few options that you will select. If you want to use the whole drive, then most likely you can just hit enter to get through all of this, but I do suggest reading the prompts before continuing.
After you finish this, and you're returned to the input line, you would then use the letter "w" to write these changes to the partition and exit fdisk. This is the step that will save the changes to the disk. It could take a few moments to run.
From here, you want to format the partition we just created. (this too may take a few moments):
From here, we'll make the directory we would like the hard drive to be mounted on, then mount it:
# mkdir /home2
# mount /dev/sdb1 /home2
# df -H
The last df -h code, should now show sdb1 mounted to home. If so, we're good to go on. If not, you probably had some errors somewhere that we'll want to take a look at
After verifying the drive was mounted, we'll add it to /etc/fstab so it always mounts. Something like this:
/dev/sdb1 /home2 ext3 defaults 1 2
Save the file and close, and you should be good to go. Please keep me updated on how it turns out.