Your image shows up, you might have to refresh the page a couple times.
The images in the atahualpa/images/header folder will rotate (either automatically or on a manual refresh). If you want only your image to show, remove the other images.
Your image is only 332x152 and that is the size it is showing.
header images will span the size of the page and are generally not too tall - I generally have my max page width set to 1440px and the header image height at 150px so I want an image that is 1440x150
How do you do this? Use a photo editing program to crop your image to the size you want to use.
When you take a photo or choose an image you should do it in LANDSCAPE mode so it is wider and only expect to use a narrow sliver of it. Think of it this way. If an 8 1/2 x 11 piece of paper is your image, you can cut a 1 inch strip from it. That is the part of the image you will use, so you have to change the way you thing about taking images. don't take close ups that fill the image since most of it will be unusable, take long shots.