From your Word help
On the Tools menu, click Research.
In the Research task pane, click Research options.
Do one or more of the following:
To activate or remove research services, select or clear the check boxes you
want, and then click OK.
To add research services, click Add Services, select or type the Internet
address for the service you want, and then click Add. The service is
automatically enabled for searching, and it will appear in the Search for list
the next time you open the Research task pane.