You can use one of the two. It will help you make banners easier than default paint program.
The banner size is 1920 x 400.
1) You open the program. You find a background image that is bigger or equal to 1920 x 400. Try to find a background image that is bigger, so you can just crop. If you used a smaller image, stretching it will make it blurry.
2) Add another layer.
3) The logo - you have to find a render/transparent/vector version. You can either find it on the official video game company's website or its social media sites. Or you can Google it. If you cannot find one, you have to make a render which can be difficult or not depending on your experience. If possible, place the logo in the center.
4) Add another layer.
5) Characters - more priority to the main characters that represent the franchise if you have their renders. Once you have your selected character renders, resize them so they are visible. If possible and you have two, put them at the opposite ends of the banner. You can arrange the characters to any position you prefer. I put them on the sides so the logo or characters don't overlap or block each other.
6) Save as Jpeg and be sure to hit yes to flatten everything.