After connecting the drive check the dmesg output. It'll tell you wether it's been detected and assigned a device name and so on. Then you can mount the device if necessary (depending on your need). Assuming it's detected as /dev/sda and your mount point is /mnt/dvdrw, mounting would be:
mount -t iso9660 /dev/sda /mnt/dvdrw
mount -t udf /dev/sda /mnt/dvdrw
Of course if it's detected as a different device name use it instead of sda, and if your mount point is not /mnt/dvdrw use yours. If you're just playing audio cds or dvd movies mounting isn't necessary, but you should still check to make sure it's detected.
Burning is another issue altogether and I don't know much about using external burners. I remember that for internal burners with a 2.4 kernel an extra boot parameter (as well as certain scsi kernel modules) was required, something like hdc=ide-scsi. 2.6 replaced this with ide-cd which is actually handled automatically. You might do some searching to see if ide-scsi is necessary for external drives. If so it could be tricky if you have other usb devices that cause the drive to occasionally be assigned a different device name.