How do you get rid of the black bars on my computer screen when I am playing a video game

just press the F11 BUTTON

Horizontal 'tears' can occur in games due to an issue in timings between the monitor and the graphics card. If your game has an option for Vsync in the Graphics options, enable it and it should solve the problem.

If that fails to fix your problem, try checking the graphics card manufacturer's website for updates to the card's drivers and the game developer's website for patches. If there is still an issue you could have a hardware fault, especially if the same bars are appearing outside of the game.