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To enable this functionality, in Mendeley Desktop, go to the Tools menu and choose "Install MS Word Plugin"
Once installed, the "Mendeley Cite-O-Matic" section will appear in the References section of the MS ribbon.
Put your cursor at the end of the document. When you click "Insert Bibliography," the reference list will appear, automatically formatted. Edit as needed, either in the Word document or in Mendeley Desktop. If you edit in Mendeley desktop and hit "Sync" and then hit "Refresh" in the Cite-O-Matic, the bibliography will automatically update.