There are two main nodes included in this shader. You can append or link them to use them in your scenes.

The "Dot Matrix Mapping" is intended to apply transformations to the image texture by pixelating it then scrolling it on the X and Y axis if needed using one of the two methods (precise offset and pixel offset).
You should plug the "Pixelated UV" output to the Vector input of your texture as follows:

The difference between the pixel offset and the precise offset is shown in the animation below:

The "Dot matrix" node takes the image, then applies the dots pattern using the "radius" and "smoothness" parameters. A radius of 1 means that the circles take the biggest size possible without overlapping, and 0 means they are infinitely small and are invisible. A smoothness value of 1 means that the dots have a transition and appear smooth, while a value of 0 makes them look very sharp.

The X and Y resolution need to be the same as the "Dot Matrix Mapping" node, that is why you need to connect the two nodes so you only have to set the resolution on the first node and see it applied on the second one automatically.

If you need to make your display monochromatic (single color), you should add an RGB mix node

The radius parameter can be variable (ie: using a texture) and can be used to create a halftone effect, just make sure it also uses the "Pixelated UV" from the "Dot Matrix Mapping" node as follows

And finally, the "Mask" output from the "Dot Matrix" node outputs only the dot pattern, you can use it if you have a specific complex material to create.