The appearance of the screens depends on the graphic theme you have installed.

I recommend you to install the theme you like and then you can customize it a little bit.

Try to make sure that the theme only requires some change of some color or some photo, not that it doesn't look anything like what you want.

from here: yoursite.com/admin/appearance/customize/css

you can add CSS commands that will be executed after loading your theme's CSS

In order to help you, you must tell us what topic you have set and ask "how do I set the background in green" or specific questions like that.

If you tell us the URL of your website, it's easier.

I am so sorry for bad English

What theme do you have installed?

What is the URL of the website?

Simplefree theme

as far as I can

 I work a lot

I have another problem

How do I remove the big picture above

thanks in advance Dave

I believe this will do it, add this to your custom css for your theme in the admin theme section

.ow_header_img {
    display:none;
}

.ow_header_pic {
    display:none;
}

You can do that css or you can go into the customization screen for the theme and remove the image in #2 header background image.

I prefer the css because that way i can leave the theme customize as default if i ever want it back.  But its up to you.

Now if you want to just change the image, i think you figured out how to do that,  just select a new image.