Multi-screen playback allows a group of TVs to jointly play a program to form a tiled display. Compared with traditional splitters, it makes fuller use of each TV's resolution and looks clearer. 
To enable multi-screen playback, follow these steps.
Create a combined screen
Bind devices following the normal process.
Create a program group, then set the group as a combined screen.
For each device in the combined screen, set the device label according to its position. This is very important.
Create the program
To use multi-screen playback, you currently need to split the images or videos into multiple smaller images/videos using a cutting tool, then assemble them in order into a program group. For a triple-screen example, you need to make 3 programs and publish them to 3 devices.
On the program detail page, click the settings icon in the top-right. Then in More Program Settings, set the program label and program group. 
Final effect: 
Publish the program
Click the Publish button in the device group list, then select the device group and the combined screen created above. 
In the publish dialog, click More Parameters to open the "Start/End Time / Priority / Playback Mode" settings.
In Playback Mode, select "Synchronized Playback" and confirm to enable multi-screen playback.
Devices with the same label will download the programs with the same label.