how to change your profiles background and banner - spacehey coding

BANNER

/*Banner*/

main:before {

    width: auto;

    margin-bottom: 25px;

    border: 0px solid black;

    height: 250px;

    display: block;

    content: "optionaltext";

    background-image: url(imagelink);

    background-position: center center;

    background-size: cover;

    border-radius: 10px;

}

BACKGROUND

body {

    background:url(imagelink);

}

please lmk if anything is wrong! im not a complete pro at coding profiles but :)