iPad Air wallpaper setup stuck at prompt

How to set a new wallpaper on my iPad air running the very latest version of the software 26. 5.2

I can select the new wall pa then click the ad button in the top right hand corner

That's where the trouble begins it appears on my screen and a bak comes up asking me if I want as wallpaper pair

select as wall paper pair

Custom home screen

I don't see any way to answer these questions and therefore I never get the wallpaper changed

Thanks

Dan