I opened the Word export and the Index page only shows a sentence about updating fields. Where is my index?

The Word index is built by Word itself from index marks in the text, so that its page numbers always match your document. When you open the DOCX, Word asks whether to update the fields in the document: choose Yes. If you answered No, or the question did not appear, click anywhere in that sentence on the Index page and press F9 (or right-click it and choose "Update Field"); to refresh everything, press Ctrl+A (Cmd+A on a Mac) and then F9. The same step fills in the page numbers of the contents page. Apps that are not Microsoft Word, such as Pages or Google Docs, may not build the index; use the PDF export for a finished index there.