Dan,
Hi. I believe that the process is to contact Matthew asking him to create a Gallery for you. That said...
When I created that Photo Tutorial, I thought that it would be a bit simpler - I would create the tutorial, folks would comment, I'd make the necessary changes, and that would be it. Now it looks like it needs to be a bit more interactive and open, which is a good thing.
Maybe it's better to have a single "Photo Tutorial" image library. For the time being, until we get this sorted out, try uploading to my Gallery and referencing the screen shots there.
I believe that we can each edit or delete the images that we create, but not delete someone else's images. I don't know if that extends to Gallery ownership.
Try uploading to my Gallery and let me know how it works out.
Thanks,
Dan.