Look at the photo. Write one leaf based on your impression of the photo, whether it be based on the content, the mood, or something you can’t quite put your finger on. Do not allow yourself to be limited by your understanding of reality.
Look at the photo. Consider what has has just happened here, or what is about to happen here. Who has been here? Who will come here and and what will they do? What kinds of interactions can you imagine? Write one leaf about these or other things that occur to you upon looking at the picture. Do not allow yourself to be limited by what you see. Go.
Write One Leaf is about writing every day. Write one leaf; one word, two pages, three notecards, four napkins, five blog posts, &c. But begin. Use your hands. The best way to get started is to get started. Write. Right now.