My multisite config not working

I have a copy of WordPress running in MAMP on my Mac. I have been using it to check my blog’s appearance before moving up onto the net. Lately, I’ve been asked by a non-profit to help them in developing their own WordPress based website. To do that, I need to install their site on my local WordPress and at the same time not muck up my blog. To that end I’ve done what I understand to be the necessary steps to enable multisite, specifically to add the line:

define(‘WP_ALLOW_MULTISITE’,true);

directly beneath the line:

define(‘DB_COLLATE’, ”);

in the wp-cofig.php file. Then, I restarted the web server. According to WordPress All-In-One for Dummies, I should log in to the Dashboard and under tools see a Network Setup link. But Since that link does not show up, I’m assuming that I’m missing a step. Can anyone help me out here?

Thanks,
Rob Tanner