How do you import a sky or background into a piece?

megagearx_eaad3c70d6

I have structures and a figure, but how does one get a sky or background into a piece that shows past a doorway, roof or window?

Sertorial

Edit > Backdrop then select a .JPG file of your choice (like a sky or rooftops or something)

megagearx_eaad3c70d6

Oh, thanks!