Monitor not showing up

need quick help. Im using a computer for monitor.nothing is showing up. I have it connected by hdmi. What am I doing wrong here.?

Unfortunately a computer or laptop cannot be directly used as a monitor as the HDMI ports on computers are output-only. in order to see the content on a computer you would need to purchase a USB capture card that would act as a video input to your computer in the same way as a webcam functions