LOL, you are not being stupid. RAR is a compression utility like ZIP. the Image is actually in the RAR. So, you will need to extract it from the file. If you google RAR, you will get the RAR site
WinRAR archiver, a powerful tool to process RAR and ZIP files
This site costs money but there is a trial. There is a better utility that is free and can handle many different types of compression utilities. It is called Tugzip
TUGZip - The Free Archiving Utility
This tool will allow you to open the RAR files and extract what is in them. Once you get it extracted, you can then burn it to a CD.
I use Tugzip at home and work. Just be sure to check the boxes to activate RAR support during the install as it is optional. After that, you can use Tugzip for just about all of your archive utilities.