OK..
#1 On You Tube right click over video's the thumbnail and select "copy image location" (I use Mozilla and in right click it offers this. Internet Exploder does not

USE MOZILLA! It's faster, safer, has more features, including built in spell checker, and it's FREE!!:dance
#2 Next, back in SBO, click the
icon and paste this image address into the address bar but first remove the
http:// that is already there.
#3 The image should show up in the post message box.
#4 Go get the URL for the video (when it's playing) from your browsers address bar.
#5 Left click on the picture you already posted into the message box and you'll see squares at each corner.
#6 Click the
icon and paste the videos address into the hyperlink web address bar, again, removing the
http:// already there.
Done...