You are going to buy a computer but first you want to do some research to you select the best model everfi answer

Ihave a singular monitor that is a tv for my computer. recently, i took apart my computer and put it back together. when i put in the hdmi cord and booted the computer to see if it worked, the computer turned on fine but the screen was blue with "hdmi no signal." i've tried everything that doesn't require buying spare parts, any answer is appreciated!