Option #1: Use /etc/fstab

In most cases /etc/fstab lists your CDROM drive so all you have do is type the following command (login as the root):
# mount /cdrom
Now change directory to /cdrom to access the contains of CD / DVD:
# cd /cdrom
# ls
The system maintains a list of currently mounted file systems. If no arguments are given to mount, this list is printed:
# mount

Option #2: Find device and mount it

Type the following command to find out your cdrom device names:
# dmesg | egrep -i 'cd|dvd'
OR directly query /var/run/dmesg.boot to get correct information:
# egrep 'ad[0-9]|cd[0-9]' /var/run/dmesg.boot
Sample outputs:

cd0 at ata1 bus 0 scbus1 target 0 lun 0
cd0:  Removable CD-ROM SCSI-0 device 
cd0: 33.300MB/s transfers (UDMA2, ATAPI 12bytes, PIO 65534bytes)

Another option is to run camcontrol command under FreeBSD:
# camcontrol devlist

<Seagate HARDDISK 1.0>             at scbus0 target 0 lun 0 (ada0,pass0)
<Sony CD-ROM 1.0>                  at scbus1 target 0 lun 0 (cd0,pass1)

You need to mount /dev/cd0 at /media/cdrom directory. First, use mkdir command to create /media/cdrom directory:
# mkdir -p /media/cdrom
To mount cdrom type:
# mount_cd9660 /dev/cd0 /media/cdrom
OR
# mount -t cd9660 /dev/cd0 /media/cdrom