When all you have is a Word file, you will first need to convert your Word document to HTML or EPUB. There are various ways of doing this and results depend on the way the Word document is laid out. The quickest way is to simply copy and paste the Word document in Joomla/Wordpress with an editor like JCE or TinyMCE, which will usually also tidy up the code. Sometimes you may lose the italics and other formatting, so be careful with this.
Another method is using a site such as https://wordhtml.com/, but often the most reliable method is to use Calibre and to convert to EPUB, certainly if you have footnotes in the text, and from there convert to HTML.
With all methods try to have your initial layout in Word as simple and clean as possible to avoid bad HTML code. Make sure in Word the main titles are “Heading 1” and subtitles “Heading 2”, etc., but if that is not practical in larger documents with poor formatting, often it is easier/quicker to convert the ‘dirty’ Word file in Calibre first and edit the EPUB conversion in Sigil. When using Calibre, it can be useful to change the default setting and to tick “Do not split on page breaks” and to set 0 instead of the default 260kb for the split threshold, then split manually in Sigil according to the chapters (
Edit –> Split at cursor).
The Calibre editor also has a useful
Tools → Remove unused CSS rules function that can clean up <span> tags and various classes without losing the italics and footnotes. Again, be careful and make sure you don't lose any formatting (you may have to get familiar with regular expressions to capture certain classes in order to convert them to italics before cleaning up).