Sounds like you were doing it right.
Try this...
1.) Click on the text inside the box
under the word Embed and hi-lite the text inside the box...as shown in the pic below.
2.) Right-click on the hi-lited text and select "Copy" from the drop-down menu.
3.) Paste the copied code into your post on the forum. (Should look like pic # 2, below)
4.) Submit your post.
Pic #1
Pic # 2
Randy