It does not have any wireless sync capability. You would need to use a wireless trigger that you would attach to the hotshoe connector of the flash or the sync port.

Basically you need one trigger on your camera to transmit the E-TTL information to the off camera flash and then you need another for it to communicate with on the flash itself.

Update: Apparently the review I found was simply 100% incorrect or perhaps it was for the first version and I missed it. As Michael Clark was kind enough to point out, it appears that the YN-622C does in fact have wireless optical sync master capability though it does not have radio sync. You only need two of the YN-622Cs if you want to radio trigger.