Şablonda HTML'i düzenle diyerek aşağıdaki kısmı bulun:

#header-wrapper {
text-align: center;
padding:0;
background: url(//3.bp.blogspot.com/-3UcLXxRcetg/WaTYDnjaJbI/AAAAAAAADt0/LL7OaZTjsE4hTzpKkm-Jj55c8JI4SZBhQCK4BGAYYCw/s1600/head-back.jpg) no-repeat center bottom;
background-attachment: fixed;
background-size: cover;
margin-bottom: 10px;
height:100vh;
box-sizing:border-box;
position:relative;
width: 100%;

background: url( ile başlayan http://3.bp.blogspot.com/-3UcLXxRcetg/WaTYDnjaJbI/AAAAAAAADt0/LL7OaZTjsE4hTzpKkm-Jj55c8JI4SZBhQCK4BGAYYCw/s1600/head-back.jpg

Sizin arka plan resminiz. Burayı istediğiniz gibi düzenleyin.