REMOVING DUPLICATES FROM iMAC PHOTS

Seems that I am not alone with this problem. Someone kindly recommended a solution if the duplicates were imported - that is what I inadvertently did! The solution was to open the imports and delete that batch - it seemed a good idea but I could not find a way of deleting 'imports'. Any ideas on how to do this or another way within the photos app would be much appreciated since Apple does not recommend third party apps for this task! Many thanks, MzeeNyuki