So click the edit button at the bottom right of your first post and change it.
It's the one that looks like a pencil and a piece of paper.
You can also check the "delete this reply" box at the bottom when editing, then click submit to delete that post. If you delete your first post in this thread, it will delete the entire thread.
For example, you could edit your first post, delete your second post. Then I could edit this post to be something helpful to you relating to your question.