Usually your EndNote software should recognize RIS files which are a standardized method to format references in a way that EndNote can import and parse correctly. Create the RIS file in your source (e.g. Zotero or a database that exports to RIS), then go to File > Import in EndNote and choose RIS as the filter type in the resulting dialog box.
If you are working with EndNote on Mac and try to import an RIS file with no success or the import dialogue box does not appear, you may need to take an extra step to associate the RIS file type with EndNote.