you should add the code to where you want the message appear.
HERE IS THE COMPLETE EXAMPLE, WITH TEXT FORMATTING:
Who is Online?
<br />
<?php $user_array = online_users(); ?>
Guests: <?php echo $user_array['2']; ?>
<br />
Members: <?php echo $user_array['1']; ?>
<br />
Total visitors: <?php echo $user_array['3']; ?>
<br />
The most guests ever was <?php echo $user_array['4']; ?>
on <?php echo date("M d, Y", $user_array['5']); ?>
<br />
<?php
for ($i=0; $i<sizeof($user_array['0']); $i++)
{
echo $user_array['0'][$i];
echo " "; // Delimiter between member names
}
?>