Okay, let me try again.
Go to the first post you made on the thread -- the starting one.
At the bottom right when you're looking at it, click on "EDIT"
It will bring up your post.
At the bottom of the box where the post is, there is a selection that says "USE FULL EDITOR"
Click on that. It will open the full post, and show you the post WITH the Title, and you can then make changes and save the post again.
I think I have it right this time, as I tried it on one of mine, and it worked.
If it doesn't work for you, just let me know what you want your title to say, and I can change it for you.
~~Diane at Castle Rock