If you want to direct members to a page other than the standard dashboard page (member.php) after they log in, then follow these simply steps.

Edit member.php

Find the following code

if(!$sUrlRelocate = $_REQUEST['relocate'] or $_REQUEST['relocate'] == $site['url'] or basename( $_REQUEST['relocate'] ) == 'join.php' ) 
$sUrlRelocate = $_SERVER['PHP_SELF'];

Change it to...

if(!$sUrlRelocate = $_REQUEST['relocate'] or $_REQUEST['relocate'] == $site['url'] or basename( $_REQUEST['relocate'] ) == 'join.php' ) 
{
   $sUrlRelocate = $_SERVER['PHP_SELF'];
}else{
   $sUrlRelocate = 'profile.php';
}

Where profile.php is the page to redirect to.