When replying to a post, choose More Reply Options at the bottom. Scroll down under the message box and select Choose File. Find the file on your computer then select Attach. Once it uploads, there is an option to Show In message or some similar verbiage. Posting this from my phone so the wording may be off a bit.
No problem. This come up from time to time and it has happened to me once too.
And to be honest, I didn't realize this thread was in the Support Tickets section until this very minute. I peruse the site using the New Content option and pay little attention to which section I am in. Didn't mean to act as if I were an admin or mod.