Yes, you will need to Initialize each of the new HDD's. Do not try to assign drive letters to them - you can't do it until they are initialized, and that process will assign letters names for you.
For a complete outline, read WyomingKnott's sticky at the top of this forum here:
Have you open up Disk Management (Run Dismgmt.msc)? It could be that your drives are not formatted, or don't even have a partition on them. Disk Management is where you initialize, partition, and format new disks.
Yes, you will need to Initialize each of the new HDD's. Do not try to assign drive letters to them - you can't do it until they are initialized, and that process will assign letters names for you.
For a complete outline, read WyomingKnott's sticky at the top of this forum here: