How is "Sync Manager" supposed to work?

I think I'm missing something basic with Sync Manager. I want to sync playlists from iTunes into RB. I use a DDJ so I'm not interested in syncing to a USB stick, just syncing between iTunes and RB

I go into SM, enable sync and select a bunch of playlists in the iTunes list. I then click the huge arrow which I believe should cause them to sync. The playlists appear in the middle section of the display with ticks against them. I close SM, and nothing has happened. No playlists are sync'd. The iTunes section of the browser now shows just the playlists I selected.

Pretty sure I'm misunderstanding something here, just not sure what. Is SM supposed to copy the playlists into the RB database, or does it just load the songs in the playlist into the database and assume I play them from the iTunes section in the browser?

Mike