sudo fdisk (or maybe better
sudo cfdisk) to create partitions on a disk. (Create partitions before formatting). With
cfdisk you can see which disks have which partitions and which disks have no partitions at all.
You may probably want to create just one partition per disk. This partition's type should be set to "83" (Linux). You may also create a swap (82) partition.
After you create a partition, you can format your partition by the command:
sudo mke2fs -t ext4 /dev/sdb4
(assuming your partition is /dev/sdb4).
Use this command with extreme care as it may probably erase all information in the partition.
If you created a swap partition use the command like the following:
sudo mkswap /dev/sdb2
(assuming your partition is /dev/sdb2).
The last but not least thing to do is to edit