If you have saved references from searches in several different databases, you will have some references that occur multiple times, because the same reference can occur in multiple databases. Using Endnote, you can remove the duplicate references you don't want to keep.
If you have a small library where you probably don't have that many duplicates, you can use Endnote's "Find Duplicates" feature. This method requires very little time but does not find all the duplicates.
After that, you can go through one reference at a time to select which of the two you want to keep and click "Keep this record"
Alternatively, you can click "Cancel" and remove all selected duplicates at the same time:
If you have a large library with many references, you may need to do the duplicate removal in several steps according to the Karolinska Institute Library's guide.
How do I delete duplicates in EndNote:
https://kib.ki.se/en/search-evaluate/systematic-reviews
A method to remove duplicate references from various databases in EndNote.