Formatting of Word Document

I need help with formatting a completed word document .docx I have a completed ebook manuscript that has been proofread, images included, page numbering and table of contents approx 50 pages. I need a consistent style sheet format throughout that makes it very easy to read using bullet points, indents, and general formatting. This word document .docx will eventually be converted for other electronic purposes such as ePub, PDF but for now I just need a good clean layout of a consistent style sheet. My preference is 1.15 spacing using arial 12pt. but open to suggestions that make it easy to read on an electronic device.