Black bars on the sides of my recordings

[runjimmyrun1]

Hey! I'm sure this is a simple fix. After making a screen recording, when I go to watch it on my media player, there are black lines to the sides. I want the recording to take up the full screen and not have black bars. What setting am I missing to fix this?

 

[Harold]

Did you set the media player you're playing the video in to play in fullscreen?