You do need to edit the Harvard output style to achieve this. To do that, you Edit>Output Style, edit output style “Harvard”. Citations section, author list - there are two settings; First appearance, which you will change to “list all authors” and the second, subsequent appearances, – by your example, you will want to change that to “2”, then list the first 1 author, but this is usually left at 3 or more. (See image attached) I would suggest that you want at least 2 there in the subsequent spot, as it is very uncommon to list only one of 2 authors as et al. Save as, and save to a new name (“Harvard-show-all-1st-appearance.ens” for example).
Then you need to use this newly edited output style in your Word document, on the Word Endnote ribbon or in the format bibliography dialog menu. Once you add a new ref or reformat bibliography, the changes should appear automatically.
One tiny problem still, the list of author names are all together and not separated by a comma or anything e.g. SotoHartmannWilkins Any ideas what the issue is?
Easiest to see if you attach your edited output style, but I would guess that there are no spaces (which are invisible in the jpg) in the “between” box?