All you need is the url plus the text after "watch?v=", so that would condense to this:
This is the standard URL format youtube uses.
Now when you're posting, there is a button for video above the message box. It looks like a small strip of film. Click that and paste the condensed youtube link (https://www.youtube.com/watch?v=PlLbBPCPLCs) into the box, then click "ok". It'll recognize it as a youtube link and put a "youtube" tag around it. This will embed the video in to the post, like this:
Age : 49 Location : Kalamazoo, MI Registration date : 2012-01-07
Subject: Re: Tech support needed Wed Mar 14, 2012 5:37 pm
Thank you so much, Pipegeek. That is actually a lot simpler than I thought.
Age : 46 Location : Centennial, CO Registration date : 2012-02-29
Subject: Re: Tech support needed Wed Mar 14, 2012 5:39 pm
No worries. If you do it once, you'll see that you can do this manually going forward by copying the URL into the text box, then just putting the youtube tags around the link. The forum software does the heavy lifting for you.