.page-name {
    margin: 0.5em 2.5em;
    color: rgb(18, 96, 101);
    font-size: 2.5em;
}

#text-box {
    position:fixed;
    top: 50%;
    left: 50%;
    width:30em;
    height:18em;
    margin-top: -9em; /*set to a negative number 1/2 of your height*/
    margin-left: -15em; /*set to a negative number 1/2 of your width*/
}