[SOLVED] How can I automatically change a URL into a link?

This new site will include a large number of www.URL.com addresses in the posts and pages. Rather than using the Insert Link for every one, is there anyway that I can tell WP or Atahualpa to do this automatically every time it sees a www? If so, can I STILL override that by using the Insert Link (for example, when I have an affiliate link)?

I found this on Codex, and tried to put it into CSS inserts, but it doesn't seem to do anything, or maybe I put it in the wrong place?

<?php make_clickable( $ret ) ?>

Also found this:

This function is make_clickable(). It works with URI, www, ftp, and email addresses. So, to linkify post content, just add the following code into your functions.php file:

add_filter('the_content', 'make_clickable');

Thanks, guys.