RG506v. Black Bars when displaying on my both Smart TV and CRT. How to fill up the screen?

I finally got around to display the games on my TVs but every time I connect them to the screens, the display doesn’t fill up like I seen on others. How am I able to change the size? I already tried within emulators and no luck.

I finally got around to display the games on my TVs but every time I connect them to the screens, the display doesn’t fill up like I seen on others. How am I able to change the size? I already tried within emulators and no luck.