The devices, which do not have any assigned account, inform the Management Center application, in a continuous mode (every 30 seconds), about it. Thanks to that you can easily connect a given device with the user account, without the need of having direct access to the chosen machine. All you need to do is find the account to which you wish to assign the given device.
If you cannot find the device on the list, you should use the Enter device IP option. After clicking Add, the information about the completed assignment of the device will appear.
In case when entering the IP address of the device does not allow for proper assignment, you should check if the Xopero QNAP service has been launched on a remote computer. If it is, you should restart or try to log in again directly from the given device to the chosen account.