Great!!!
So you'll create your document at 144x48 inches, at 150ppi, in RGB mode, and the sRGB colour space.
Your choice here will depend whether there ends up being text or logos or any linework in your design. If it has those things, you'll use PDF. If it's only photos, you'll use jpeg.
Important information about PDFs here: https://www.damiensymonds.net/2010/05/making-pdfs-from-photoshop.html
You don't need to worry about this. The act of saving as a PDF does this automatically.
Needless to say, please write to me again any time you need help.