You can make a logo with name logo.png and then override templates/smart_news17/images/logo.png
If you want to use another name, please upload that logo to templates/smart_news17/images/ folder, and then open templates/smart_news17/css/template.css file, find this code
#yt_header h1.logo a{
background-image:url(../images/logo.png);
background-position:top left;
background-repeat:no-repeat;
height:64px;
width:273px;
display:block;
}
and change logo.png to your logo