Sorry to waste your time, all. I have photos but can't seem to figure out how to add them to the post.
When you're writing a post, click the button on the bottom right that says "upload a file," and then add the photo from your computer. Once it's uploaded, and before you click "post reply," click on "full image" so the photo appears in your post rather than merely as a thumbnail attachment.
I figured that is what I should be looking for, but there isn't an "upload file" button visible, perhaps because my new membership hasn't been confirmed yet (although I do have a profile page, etc)?