Having posted, you should be able to edit your post. There should be a button that says "edit message" to allow editing. Are you asking how to post a picture?
今は紅葉は素晴らしい、日本で。
I use Flickr to store my photos, and link them here using the "bbcode" option. In Flickr, click on the "arrow" icon to share the picture, then select "bbcode". Copy the text, then paste it into your post here, and save the message. You'll then see the picture like this:
Kenroku-en Maples by
RobGeraghty, on Flickr
My Japanese probably isn't good enough to explain in Japanese. すみません。