The Mail Merge Helper may not be readily available in Word, but you have to manually add the icon to your toolbar in order to use it.
  1. Select Tools > Customize , and then click the Commands tab in the Customize window.
  2. In the Categories list, select All Commands and then select MailMergeHelper from the Commands list.  
  3. Click the MailMergeHelper command and drag it to the location where you want it to appear on your toolbar.   
  4. Click the Close button.