Add the following to config/config.php.

define('AK_LOG_EVENTS', true);

Optionally, define the log directory in config/config.php.

defined('AK_LOGS_DIR') ? null : define('AK_LOGS_DIR', '/path_to_logs_dir');

Note that the following should be left as the last line in config/config.php to avoid “already defined” errors.

include_once(dirname(__FILE__).DIRECTORY_SEPARATOR.'boot.php');