How can I change header images in categories and remove the “category”

Hello everyone,

I am trying to change the header image in each category, but I can’t do it.

I cannot find an option to either remove the header image or add a new one.

I installed the “WP header image” plugin, but it let me only choose some default images, and I couldn’t find a way to add new ones.

I am also trying to remove the “Category” text from the header image, as well as the “test 6” text, which is a title of one of my test posts.

I have deleted my cache and also my browser history and cookies, but it didnt help.

I am a bit confused ??

Any help would be greatly appreciated ??

The page I need help with: [log in to see the link]