I apologize for my ignorance but at least is curable.
This is what I'm trying to do
Example:There is a new thread in the SL forum that is very similar to one that was posted before a couple of years ago by me with positive results,and I really apreciate the help. How do I use the old thread to reply to the new one? I see other members do it and I like to help others the same way I was helped,but do not know how to make the shortcut or link to the old thread as part of the reply

1) Go to the old thread that you want to link to and copy the URL that's in the address bar of your browser.

2) Go to the new thread and click reply.

3) Insert the link to the old thread by clicking the little icon that looks like this: http://www.mercedesshop.com/shopforum/images/editor/createlink.gif
Paste the URL into the popup box and click ok.

Thank you.