a-child

Hello,
I run a demo copy of WordPress at the URL https://www.knowk.com/nwpb/
So far I have created an Atahualpa theme child and named a-child,,, so at least the basic example was clear enough.

I now have no clue on what to do for letting the installation override the instructions to use the images which I want, instead of those given by default and switching back on each new updating of Atahualpa theme.

Of course I’ ve placed the wanted images in a folder’s path as they are set in the Atahualps suite and set them via FTP on website:
Path: /www/nwpb/wp-content/themes/a-child/images/header/

Can anyone help by telling me what to do to let my installation use them instead of those contained in the updating files?
Thanks a lot ??