I have to offset "normbs" 1/2 star rating a little. I have to admit I never looked in the manual. To "sync", just press on "New", choose Sync and choose a Wuala and a Local Folder to sync.
I agree that Dropbox is easier to use, but Data is only encrypted on Dropbox Servers and Dropbox has the key, so they can decrypt it if they like. Wuala encrypts on the client, and Wuala has no key - so it's a lot safer. Wuala claims they could not decrypt, well, there is no proof this is true but it should be safer than Dropbox. Their servers are in switzerland and france, so they are not under the us "patriot act", which is important especially in europa, because basically it is illegal to put any privat data from other people (clients, friends...) on a server where the US government could spy at if they like in most european countries.
Also, you can sync any folder you like at any location, not only a Dropbox folder. Besides Syncing, Wuala also offers the possibility to backup folders. And then, many LaCie Harddiscs offer promotion codes which give you free extra storage.
So all in all, I think it's worth to look at, even if I have to agree that the interface could be improved and dropbox is a lot simpler.