If you wish to add additional referencing styles, you can use the Style Finder to search for a style name and/or citation style and/or publisher. 

Irish Historical Studies: TCD have now added a version of the IHS Style to Endnote. It does come with the warning "This style is for the Irish Historical Studies journal as adapted for use by the Department of History at TCD. This is a very challenging style to automate and some aspects may need to be done manually, after converting a document to plain text."

To access go into "Additional Resources" and go to "Output Styles" and select / download the IHS Style to Endnote.

Most databases have a direct export function to EndNote but for some its a little trickier. This is particularly the case with some Law Databases.

WestLaw: No direct export, but can import the PDF. If no Digital Object Identifier (DOI) you may need to fill in fields.
 

HeineOnline: 
Register with MyHein, Bookmark Articles & Export to Endnote or within the “Law Journal Library” click the Cite button & Export to EndNote
 

Vlexjustis: Use Share (RIS EndNote) to export Journal articles.
 

Lexis+UK: Export the Bibliographic Records in RIS format & then Import into EndNote
 

EndNote support contact: EndNote support  EndNote.support@clarivate.com 

EndNote Click -- formerly Kopernio --  is a free, easy-to-use browser plugin that helps you save time accessing full-text journal articles by bringing your institutional subscriptions as well as open access content into your workflow at your point of need.