It is very easy to add harvard referencing style to Microsoft word. Just follow my steps to do it.
Firstly, download the styles from Github as a zip. Open the zip file and extract.
Secondly, copy and paste the styles you want from the folder to your MS World style directory.
My MS Word style directory can be found in:
C:\Program Files (x86)\Microsoft Office\Office14\Bibliography\Style
I have pasted the harvard style and my folder looks like this:
Lastly, close any existing MS Word projects and Open MS Word as an administrator. Click on the References tab and Style option as shown in the Image below. That’s it, now you can choose the newly added bibliography.