Place your cursor in your Word file exactly where you want the citation to appear. Click the Insert Citations button on the EndNote toolbar in Word and enter a keyword to locate your citation, then click Insert. The default in EndNote is Cite While You Write, which means your citation will be formatted and a bibliography generated automatically.Each time you add another citation, EndNote will re-generate the bibliography to add the new reference.
Here's what the Word Mac 2011 toolbar looks like
(Image from: http://www.eui.eu/ServicesAndAdmin/ComputingService/Software/TutorEndNote.aspx)
Here's what the Windows Word 2010 toolbar looks like:
Select the references you want to include in your bibliography, then on the EndNote menu, click References / Show Selected References.
On the EndNote menu, click File / Export… then choose a file name. Save as type Rich Text to create a Word-compatible file, or HTML to create a web bibliography.