3 ways.
1> Get a squirrelSCSI and an external CD drive
2> If you have a Blizzard accelerator in your 1200, you can install the SCSI kit that comes with it which will let you hook up external devices.
3> cut a hole in the case and install a laptop CDdrive. You'll need to buy an IDEsplitter which are available at Amigakit.com Others on this site have done this, so just take a look in the photo section.