In all editing modes that I've tried (basic, advanced, and WYSIWYG) there's a control for inserting links. It's located above the text box and looks like this:

To use it:

1. Type in the word(s) that you want to show -- for instance, "here".

2. Locate the URL that you want to use with it and copy it to your clipboard -- for instance,
http://forums.psychcentral.com/misc.php?do=bbcode#url

3. Highlight the "here", click on the , paste your URL into the dialog box, and click [OK].

here

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edited to add:

What that button does, of course, is insert the BB Code for a link, like this:

If you use one of the text editors, you see the actual BB Code tags in the text box. If you use the WYSIWYG editor you just see the result.

I put that code in a "Code:" box so my browser wouldn't show it broken into two lines.