Trying to add a file (scanned image) to an existing thread. Went to FAQ to add a file to my response.

Answer said "When creating a new thread or response, you'll see a "File Manager" link on the "Full Reply" or "New Post" page. When selecting this option you'll receive a popup which will allow you to attach files to your post."

Using the full reply, I can't find the "File Manager" tab. What am I doing wrong? Thanks