Hover your mouse over the menu options to display their function.
Make sure your EN library is open as well as your Word document when using CWYW.
When you install EN it will automatically install files allowing EN and Word to communicate and enabling Cite While You Write (CWYW).
In Word 2007 and later versions you will see a tab on the ribbon with the version of EndNote you are using.
Select this tab and the EN menu will be available to you.
On a Mac it will display as a floating toolbar which you can reposition on your menu bar or elsewhere on the page. The menu options are also available from Tools on the Menu.