hi steve - on your completed posts you should see an edit button. you can click that and edit your post or the subject and click save.

if you don't see what you want to change after hitting the edit post button, you'll see a go advanced button.

click that one and you can edit the title. I don't know how long that edit title function is available though.

That will give you more options like delete an attachment, add one, add smilies, etc.