It seems to me there are two ways to go. You can either take your material and shop for a publisher or you can self-publish. Both of these have pros and cons. I think it really comes down to how much you are willing to take on yourself versus how much of the project you want to hand off.
For example on one end of the spectrum is the totally indie, do-it-yourself, self-publisher. Someone that takes responsibility for designing the e-book, getting it on the various e-book platforms, various technical aspects, pricing, marketing, and anything else that comes up. On the other ends is someone that doesn't want to touch any of that. They want to find an agent, that will find them a publisher and they will adapt or change the material to suit them.
I suppose there is a middle ground where you could partner up with an illustrator or a producer that might help create the project. So I guess the first step would be to figure out what you are willing to take on and what you need to "shop out".
Are the storyboards actual rough page illustrations and layouts? Does this book have any interactivity?