To burn an ISO image to a CD from the graphical environment, start up the finder and browse to the directory where the image resides. Right-click on the image file, then select "Open with..." --> "Disk Utility". This will open the disk utility window. Now click on the ISO image on the left-hand side of this window and then click the "Burn" button at the top left (the button with a menacing black-and-yellow radiation symbol on it). You'll be asked to confirm the automatic choice of burning device, and then Bob's Your Uncle.
You can accomplish the same thing from the command line, using the drutil command. For example:
drutil burn -eject filename.isoUnless told otherwise, drutil will choose the first available CD burning device, and write the image to that. Command-line switches allow you to choose a specific burning device. The command
drutil listwill show you a list of attached devices.