Before we start the synchronization with booking portals please make sure that you have adjusted and that you feel comfortable with such settings as room and rates, adjusting prices, booking methods and its commissions. 
You can find the tutorials depicting configuration of this settings over here: 
Rooms: http://vimeo.com/26443387
Pricing: http://vimeo.com/26443953
Booking methods: http://vimeo.com/26480847

You should also enter the reservations that were made before the moment of synchronization and are still valid.