So if I understood your issue correctly you want to edit your output style, and then in the Author Lists settings, in Bibliography, select “List all author names”. I have included a screenshot.
However I’m using Endnote basic, as in Endnote Online through Web of Science and I can’t seem to find the tool bar, tabs and drop down menu shown in your picture.
I’m afraid I just can’t access those features in my Endnote version…
How stupid of me. Unfortunately I don’t have any experience in Endnote Online, but after some research into it I believe it isn’t possible to edit output styles at all in Endnote Online. Do you happen to have access to the desktop version of Endnote through an institutional login?
I suggest you download a trial copy of Endnote! You may discover it is worth the money at a later time, but in the meantime, you can edit and format your document.