How do you use a Lenovo AIO as an external monitor? Well, I must say it is not easy since Lenovo has quite a few model lines and configured them a bit differently so owners and users who knew one way are stumped when it fails to work on another system. Second, the source can be from a computer, laptop, game console, or another AIO that is daisy-chained and the proper casting must be used to prevent a no signal.
Windows to Lenovo AIO
As you are utilizing Windows, you will need to use the screens mirror or extended feature to cast to the Lenovo AIO. The Lenovo AIO needs to have at least one video IN port (usually HDMI since it carries audio and video in one) but you may have a Lenovo AIO that only accept a VGA signal and has to run an additional cable for the internal speakers or utilize external ones.