S! all, you almost had it right in your first post, but you had the [youtube] and the [/youtube] reversed.
You need to copy the url: http://www.youtube.com/watch?v=a7wBwKY9 ... 46DE34D315 and place it in between the [youtube] and [/youtube] ---- (the [/youtube] part goes at the end of the line, not at the beginning of the line), IE:
[youtube] http://www.youtube.com/watch?v=a7wBwKY9 ... 46DE34D315 [/youtube]
*** note - I placed a space between the ] and http: and between the 34D315 and [ in the link directly above so you can see what it should almost look like to post the video; when you paste the url address, do NOT put a space after the ] or before the [ in the line like I did above so you could see it; there should be no space after the ] or before the [.