How to change the content of other computers by using one PC

Question

Hi just wanting to know if you can help me. Basically I own multiple shops and in the window of each of the shops is a TV and it is connected to a PC. I want a software that I can load to all the PCs and then be able to change the visual image on each particular TV from our main office either by software or a website. But I need it to have a log in so that Only TVs linked with that log in appear when logged in.

I want to develop an application in windowsForm or website C# to change the content of other systems.