You mean like this?
The Three Caballeros Trip Report
There are two ways to do it. The first is to manually type it out, like so:
?URL="http://www.disboards.com/showthread.php?t=1405215"]The Three Caballeros Trip Report[/URL?
Replace the first ? with [ and the second ? with ], and of course make sure the URL is correct.
Or simply highlight the text you want to turn into a link, then click on the graphic at the top of the input box that looks like a globe with a chain under it. Enter the URL in the popup box and click Okay. You're done!
*Brian*