EndNote allows you to select and change the citation style of references in a document. The EndNote toolbar displays the current style, and the drop down arrow will reveal other popular or recently used styles. The Select Another Style option opens a pop-up with the hundreds of citation styles that come with EndNote.
Changing the citation style in Word will automatically refomat all the citations and the bibliography according to the new style's rules.
Sometimes, you may need to edit an existing citation style to customize it for your exact needs. This could be as simple as adding page numbers to an in-text citation or using a full journal name as opposed to an abbreivated title. The below links and documents illustrate downloading, editing, and creating new output styles.