HMTL CODING FOR SQUARE SPACE WEBSITE

Can someone that is familiar with Square Space and also is good with HML codes advice me on how I can change the header image on of of my 5 pages.

Should be a quick job for someone who knows there way around Square Space.

This is the layout of the normal headers:
http://pauline-skewes-9y0a.squarespace.com/

This is the page I would like to change:
https://pauline-skewes-9y0a.squarespace.com/blog/
(I have already managed to put the image I would like to use as the header instead which is the top one. The image I would like to get rid of is the one below that)

Thanks.