The LED Screens can be controlled remotely. There are many variations of technology that are used to send the imagery to the screens remotely. Some use RF, GPRS or 3G/4G or any other network technology to connect and upload the image files. The internet can be used to connect to the screen. There are proprietary software or generic software such as LED Studio that are used to program the screens.
One can use a desktop or a laptop using internet or some other connectivity to connect and upload the image files to the screen.