Endnote comes preloaded with a few popular citation styles (called Output styles in EndNote) on the EndNote Toolbar. The style you choose will change the way your in-text citations and bibliography are formatted in your Word document.
To change the output style in your Endnote library:
If your style is not listed on the toolbar, browse the Output Styles List for it
Looking for AMA Citation Style?
Select JAMA from the Output Styles List