If I understand you correctly, you would need to create a partition on sda (if that's your new drive), copy all the files from /home into that partition, then edit your /etc/fstab file to mount /dev/<new partition> as /home. For example, my fstab:
Code:
#
# /etc/fstab: static file system information
#
# <file system> <dir> <type> <options> <dump> <pass>
devpts /dev/pts devpts defaults 0 0
shm /dev/shm tmpfs nodev,nosuid 0 0
/dev/sda12 /boot ext4 defaults 0 1
/dev/sda5 swap swap defaults 0 0
LABEL=ARCH / ext4 defaults 0 1
/dev/sda6 /home ext4 defaults 0 1
Here, I'm mounting /dev/sda6 onto /home with the ext4 file system - you'd replace sda6 with whatever the name of your new home partition is.
Hope this helps,