How to Add a Sub Index in Office Word

1. Open a document in Microsoft Word that you want to index.
2. Highlight a word or phrase in your document that you want to use as an index entry.
3. Click the 'References' tab. Click 'Mark Entry' in the 'Index' group.
4. Type a word you want to use as the main entry for the word or phrase you marked. This could be a more general heading, such as 'Writing.'
5. Type a word you want to use as a subentry. This is a more specific entry, such as 'fiction' or 'short story.' If you want to add a third-level entry to the index, enter a colon after the subentry text and then type the text for the third-level entry (something that falls underneath the subentry).
6. Specify the page number format that will display in the index.
7. Click 'Mark' to mark the entry. Click 'Mark All' if you have more than one occurrence of this entry in your document.
8. Repeat the above steps to add additional entries.