VGA Port on my new computer?

So I bought a brand new computer, an HPE 400-f and the only input for a monitor on the back is an HDMI input. My monitor only has a VGA output on it, so I needed a VGA port. I noticed that there was two input port that were covered by metal coverings that said, "Do Not Remove." One of them seemed to be the shape of the input port I needed, so I unscrewed it (there was just two screws and it came off easily) and there was a VGA input there. So, I plugged my monitor into it and turned on the monitor and the computer, but the monitor still said no signal even though it was hooked up. The problem is not with the monitor because I tried it on two other monitors (all with VGA output) and none of them worked. I was wondering if there was something I needed to do to get the computer to output to VGA, or any other ideas.