The synchronisation process allows the user to transmit the current configuration to thousands of devices with a single click. To do this click on the user name (top right corner) and then click on Synchronise.
It is an automatic process but not immediate, as it may take a few minutes before you see the changes on the Advertisim device. You will see a message indicating the number of installations affected by the changes you have just synchronised. The devices are now configured to start playing the content.