GNS3--How can I access it

in CCNA & CCENT
I have used Packet tracer, but I would like to work with GNS3. But as I understand it, you need an actual IOS along with the GNS3 platform. I am guessing if I don't have an IOS, I would have to purchase that. Where can I find info on how to get access to an IOS once I have installed GNS3? Thanks for any help in advance.
Comments
Any other means are not to be discussed here.
The forum post was not meant to do anything unethical. I simply did not know that was the only means. Thanks.