Attach an HDMI Cable
This setup is similar to using dual monitors on Windows because you’re using a cable to add a second display to your laptop or desktop.
Plug In a Chromecast or Roku
In many cases, someone wants to connect a computer and projector for a particular reason, like watching a movie or showing pictures or a presentation, not necessarily to project the whole computer screen. If this is your situation, a streaming media device like Chromecast or Roku is easy to set up and works if the projector supports HDMI. If you’re in a school or office, there’s a good chance there’s already a cable coming from the projector that you can plug into your computer.
PC screen only (called Computer only in Windows 7) essentially disconnects your screen from the projector—don’t choose this one.Duplicate will do just that: show the same thing as what’s on the computerExtend turns the projector into a second screen, letting you drag items between the two.Second screen only (called Projector only in Windows 7) shows everything on the projector and nothing on your computer.
Miracast Could Be an Option
Some devices support wireless connections via Miracast, which is much more convenient than a cable for ceiling-mounted projectors. However, it’s likely not supported by as many projectors as Chromecast. For example, if you’ve got a Chromecast and want to project your computer screen, it’s as easy as using Chrome’s built-in Cast feature—it lets you show a specific tab, your whole screen, or a file on the projector. If your computer supports Miracast (more on that below), you can use screen mirroring on a Roku. Check this list of Miracast devices to see if both your PC and the projector are supported. If you’re still not sure, walk through these steps to see if it works.