It is possible to use your EndNote Online library to insert citations as you write. To convert the EndNote tab to an EndNote Online tab in Word:
1. Select Preferences in the Tools group of the EndNote tab.
(Mac: select Cite While You Write Preferences... from the CWYW drop-down on the floating EndNote toolbar in Word for Mac)
2. Select the Application tab and select EndNote Online from the drop-down.
3. Enter the required login information and select OK. You are now able to search and insert citations from your EndNote Online library.
If you don't already have an EndNote Online account you can create one from within EndNote desktop (e.g. in X7.3: Edit menu, then Preferences, then Sync).
Note: There is no Insert Citation drop-down with EndNote Online, and Insert Selected Citation(s) and Find Figure commands are not available. Instead you search your EndNote Online library via the EndNote Online Find & Insert My References dialog (Mac: Find Citation(s) button on the floating EndNote Online toolbar in Word for Mac).