InDesign - Setting Up A New Document

File > New Doc

INTENT

Web - Only seen onscreen
pixels and RGB

Digital Publishing - For Apps

Pixels and RGB
Page size is device

Print- Print AND Onscreen

Number of pages?

Facing Pages - For brochures, books, magazines

Not Facing Pages - For one page or double sided, single sheet documents.

Page Size?

Number of columns?

Margins?

More Options: Bleed. 5mm for most cases, but you should check with your printer.