Set them in the MD before you upload, because the converter copies the title and author stored in the file. In Word, fill them in under File, Info, Properties; in Markdown, add a YAML block with title and author at the top; a PDF uses its own document properties. A plain text file stores none, so its file name becomes the title. There is no metadata form on this site, so details such as an ISBN or publisher are added afterwards in an ebook editor like Calibre or Sigil, or in the store upload form.
Italic and bold text carry across. Straight quotation marks are turned into curly typographic ones and double hyphens into proper dashes, so the EPUB reads like a typeset book. Page size, margins and page numbers are not kept, on purpose: a reflowable EPUB has no fixed pages, and each reader app lays the text out for its own screen.
