Question / Help how to remove black bars

[takyx]

i have black bars on the side of my stream and its annoying i know i can stretch to screen on game capture but i can't use game capture as i use osbuddy a runescape client, even when i try doing it with my browser game capture doesn't work idk if its wrong on my end but yeh besides that i use windows capture and id like to stretch my screen so i don't see the black lines to the sides of my stream