Posts don't need to be actually posted to the board to see what they'll look like--e.g., did my dog's picture come through? They can be tested by hitting the "Preview Post" button, under the icons, next to the "Add Reply" button.
If the post doesn't appear as expected (e.g., pictures don't post), the post can be edited as necessary. The "Preview Post" button can be used after each adjustment. Once the posts looks the way it should, *then* hit the "Add Reply" to post to the board.