When you need to "stage an opening," you can't beat a gatefold design. It's dramatic, and it grabs the reader's attention.
The gatefold brochure is created from a legal-sized sheet of paper.
The "gates" in the gatefold design stand side-by-side, but when you produce the layout on your computer, they're on opposite sides of the screen.
If you want to let a single image span the gatefold, you first place it, clone or copy-paste it, and line up the two images. You can crop it if you feel the need to, although the printing will do that for you.
Remember that printers don't print a bleed . . . that is, for a continuous image on your gates, you will need to trim the page. You must allow for that in setting up your pages.
To create a gatefold brochure:
Although you set up the file as two pages, think of it as a four-part layout:
the "gates" panels (which work together as if they were a layout in their own right)
the inside of the brochure (four panels that work as a single spread).
The same image, positioned twice, will produce a single image when the gates are folded together.