Terence,
I created an image file that is 1152px wide by 120px in height, then uploaded it under appearance > header. One other thing I learned is that you also have to make sure that the “show title” check box is unchecked under the themes > customize section, otherwise you’ll get the header text overlay on your logo.
Then, depending on the width of your logo, you have to update this CSS code, as follows, note the change in width from 50% to a specific size of 290px.
.header-image #title,
.header-image #title a,
.header-image #title-area {
display: block;
float: left;
min-height: 120px;
overflow: hidden;
text-indent: -9999px;
width: 290px;
}