Hello Ken,

Go to Step 1 General Settings > Template Style > Template Structure...  select 'Header' from the 'Page Section' drop-down menu.

In the 'Image File' field you will see the name of your header image, which in this case is 'top.jpg'  -  right-click on this field and select 'Open file location' from the context menu.  This will open the folder where the image is stored on your computer.

You can edit this image using any image editor of your choice...  e.g. use Microsoft Paint, or alternatively the freeware paint.net:

http://www.getpaint.net/

When editing you might want to take care that you don't distort the aspect ratio of the original image.

Once you are happy with your changes you can save the file again.  If you decide to rename it then you will have to set the 'Image File' field to point to the renamed file.

At this point you might also want to adjust the header height, as shown in the screenshot attached.

Kind regards,

Paul