Domain Mapping plugin

I have installed the Domain Mapping plugin and have installed it as requested (moved sunrise.php and added the line define('SUNRISE', 'on'); to wp-config.php) but my Domain Mapping Mapped Domain tab shows no sites there for me to map. I need to point paxlibertas.com to my site ID 1 (paxlibertas.wpengine.com), but I have no option to do that. I'm not sure what I've missed.