pnb2017,

Try the steps below.

1. Press Windows + I to open Windows settings.
2. Click "Personalization"
3. In the side bar, select "Lock screen"
4. In the lock screen settings, select "Picture" (always the same image) or "Slideshow" (alternating images) as background.
5. If you selected "Picture", you can click "Browse" to find and select your picture.

Thanks but why is a 'picture' included in the Slideshow setting? Surely that is a fault?

Peter