You can use the following steps to make the change:
Click on the citation you wish to change.
From Word’s Tools menu, go to the EndNote submenu, and select Edit Citation(s) to display the EndNote Edit Citation dialog. From the EndNote tab, select Edit & Manage Citations.
All of the cited references in the document are listed in the left column of the dialog. An ellipses shows where a citation appears within text. The line below shows the cited references.
Select the appropriate citation from the list at the left of the dialog (you can scroll through all citations in the document) and make any of the following changes to the highlighted citation:
Display as: Author (Year): Select this menu option to display both the author name and the year in the highlighted citation.
Click OK to implement your change(s).
If you do not have the option for Author (Year) you would need to switch your tab in Word:
You cannot change all at once but you could edit a style to make Author(Year) the default.
See our website for a guide on editting styles