You will find "Upload new EJS jar file." check box, at the same line where you find "submit" button when you edit message.

Click the check box, then select the EJS jar file from your computer (the same file you have attached in the previous message).
Then click the submit (Post) button, and you will find simulation displayed as part of forum message.

You can update the jar file,too!( when you edit the message)
Please try it.  ;D