Your installer may just have an option to set this up (I believe debian does does) You just need to get your extra disks/partitions prepared. You can use gparted to create partitions on the drive. If you do not have the option during install, you can create the partition and move the files manually, then edit the /etc/fstab file to automatically mount the partition at /home. Here is a quick guide, but there is tons of information on the fstab file on the internet.