Only in the Windows version. Here is the help topic – Noticing it only says compatible to 2013, but they do miss updating help often in new versions… It appears on the ribbon of PowerPoint in 365/2016 anyway. It is pretty rudimentary.
Introduction to PowerPoint
Introduction: Inserting Citations and References in PowerPoint
Use the commands at the top of the PowerPoint ribbon to easily and quickly insert citations and references in your PowerPoint slides. EndNote formats citations and references based on the rules defined for the selected output style.
We recommend that you select a style from the Output Styles menu before you begin inserting citations and references in your document. Please remember that selecting a new output style will not update the formatting of citations and references already inserted into the document.
This feature is compatible with Microsoft PowerPoint versions 2007, 2010, and 2013.
Insert Citation
Select this option to search for and insert citations in your document. Selecting this option opens the Find & Insert My Citations dialog.
Insert Selected Citation(s)
Select this option to insert selected citations from your open EndNote library. First, open EndNote and select the needed references from the Library reference list. Return to your PowerPoint presentation and click this button. EndNote inserts the citation for selected reference where you position your cursor.
Insert Reference
Select this option to search for and insert references in your document. Selecting this option opens the Find & Insert My References dialog.
Insert Selected Reference(s)
Select this option to insert selected references from your open EndNote library. First, open EndNote and select the needed references from the Library reference list. Return to your PowerPoint presentation and click this button. EndNote inserts the selected references where you position your cursor.
Output Styles Menu
Use this menu to select an output style from the Style menu before you begin inserting citations and references in your document.
Go to EndNote Command
Select this option to open EndNote if it is not currently open. If EndNote is already open, this option brings EndNote to the front of the screen.