EndNote & EndNote Online

How to install additional styles:

1. Download the style

2. Double-click the style file.  It should open in EndNote

3.  On the open style, go to “File Menu” and choose “Save As”.  Replace the word “copy” with your style’s name and click “Save”.

4. Click on “File Menu” and choose “Close Style”

5. Then Go back to your EndNote Library and go to "select another style". Choose it from the list

Where to save your styles:

The 400 styles which come with EndNote are usually located in this location.These can stay here:

C:\Program Files\EndNote\Styles

Any extra  styles will need to be saved outside of your Program files, into your personal styles folder.  EndNote will then merge these folders into one list when you go to choose a style.
To find the correct folder location for your personal styles folder, first open EndNote and look in Edit>Preferences>Folder locations.  This will tell you the default file path.  The first time you should create the Styles folder following this pattern. 
It will look similar to this:

C:\Users\UserName\My Documents\EndNote\Styles

Save any modified styles you download into your personal styles folder