You posted that already above, that alone won't help. And you can easily attach the file.
Below the forum editor (only available in Full editor, not via quick reply), switch to the tab "Upload attachment".
Upload your file, then when finished, click in the editor window where you want your file to display, and click the button "Place inline".
And you are intended to run this command: viewtopic.php?p=60384#p60384