Welcome Ken.
Great to see another site to add to the network. If you can add a link to your site to your profile it’ll help other people map your site to your posts.
There is obviously no requirement to have any experience selling through the agencies, but if you are not familiar with the issues of what is and is not OK for selling with a royalty free license, I’d strongly suggest that you use the agency’s training materials to bring yourself up to speed – you don’t want to find yourself on the wrong end of a lawsuit 🙂
I didn’t write the post with this in mind, but I have a recent blog post that has links to agency training as well as some general (if very brief; it’s an overview) guidance
http://www.digitalbristles.com/fiverr-sellers-top-10-tips-for-stock-image-gigs/
The links to iStock and Shutterstock’s guidance in number 9 are helpful – iStock’s is very thorough.