​If you think your manuscript is ready for submission and discover that your dream publisher(s) only accept agented submissions, or if you're ready but you just don't feel like you can handle the contract side of things, it's time to start hunting for an agent, and these sites can get you started on your way.

AAR
Agent Query

I'm not endorsing any one of these publishers, just sharing the info for those of you who might be ready to start submitting your own work into the wild world.

Kensington Books
Ballantine Books
Avon
Harlequin
Entangled Publishing
St. Martin's Press
Hachette Book Group
Penguin

Even when a story doesn't have a mythological basis, I am a huge mythology buff, and these are a couple of good sites to learn more if you are interested in myths, too.

Encyclopedia Mythica
Greek Mythology