You'll need a SCSI controller and a SCSI CD-RW drive.
Alternatively you'll need an IDE controller and a compatible IDE CD-RW drive.
Of course you will need the appropriate cables, and screws for securing it inside the case.
What type of drive you chose depends on what type of controller you have. I assume you have some kind of existing controller, since I (again, I assume) assume you're talking about backing up artwork you already have saved on your internal hard drive.
Everything you need can be bought on ebay or Amibay.
You'll need the MakeCD software (google it) which AFAIK is the only software for Amiga's that can write files to a CD. I've used it, it's a bit slow, I don't think it will work at all if you only have a 68000 (unaccelerated) CPU. Learning curve can be tricky.
Setup is easiest under Workbench 3.9. A bit harder under 3.1. A right royal PITA under 2.1 or anything older. Obviously this is IMHO, maybe some folks like to torture themselves by setting them up under 1.3.
Not to dissuade you, but if you've never before installed a drive in an Amiga you're going to have to do lots and lots of research, to learn how to set this up. Good luck!