Open your Word document
Place the cursor where you want the index
Go to the References tab
Click Mark Entry
Select the text you want to include in the index
Edit the entry if needed
Click Mark or Mark All
Repeat for all index terms
Place the cursor where you want the index page
Go to the References tab
Click Insert Index
Choose the format and options you want
Click OK
Update the index when needed by right-clicking it and selecting Update Field