Use the "Edit and Manage Citations" button on the Word Toolbar to change how a formatted citation appears in Word, or to add a page number inside the citation.
For example after inserting a citation
to change to
1. Highlight the citation in Word
2. On the EndNote Word Toolbar, Click on "Edit & Manage Citation(s)" (or simply right+click on the Citation)
3. Select "Display As: Author (Year)"
4. Note: This will change the highlighted citation only, others will be unchanged.