You need to be sure you have version 1.2.9 (or later) of Lightshow installed. See this page for update info and for instructions on how to update your script:

http://www.projectseven.com/support/updatepages/lsm.htm

Just make an ordinary text link anywhere on your page. Select the link and open your Behaviors panel. Open the Behaviors menu and choose:

Studio VII > Lightshow Magic > PVII Lightshow Magic - Control Table of Contents

Select which Lightshow to use and the Action you want to take.

If you look at the markup for the "Launch Table of Contents" link above, the code looks like this:

<a href="#" onclick="P7_LSMtoc('show','p7LSM_1');return false">Launch Table of Contents...</a>

I've placed a second link right here:

Click to launch TOC