Header image issues

Hi,

I’m attempting to change my header image. I had this problem a year ago, and was told to use the dimensions 1007 x 199. Soemhow I was able to make it work them. When I set the dimensions at 1007×199 for the new image, what displays is the upper corner of the entire image. I tried using much smaller dimensions, which resulted in the display showing a lot of squares. When I changed the dimensions to 8000 x 600, the header only displays the upper 25%. In the video tutorial, the image that is left after cropping is exactly what is displayed. Why am I not getting that result? What can I do to get the image I want? Thank you.

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