/dev/ad[Number] represents IDE drives
/dev/da[Number] represents SCSI drives
You may use /stand/sysinstall --> Configure
FDISK -> Select "A" for entire disk
LABEL --> Select "C" to create new partition, size and mount point --> Exit from this menu to save changes
OR
Through the command line (CLI) with these commands: (Replace /dev/ad2 with appriopriate entry)
dd if=/dev/zero of=/dev/ad2 count=2
disklabel /dev/ad2 | disklabel -B -R -r ad2 /dev/stdin
#Multiple partitions
disklabel /dev/ad2 > /tmp/label
Edit disklabel to add partitions: vi /tmp/label
#Assuming only one partition
newfs /dev/ad2c
This was written as a basic guide - Any suggestions or comments are welcome!