Unlike in Word for Windows, there is no reference tab with a link to EndNote in Word for Mac.
There are a couple of ways to access EndNote from within Word on a Mac.
The first way is to choose Tools at the top of the page, and then select EndNote.
The other way is to choose View at the top of the page, select Toolbars, and then EndNote. This will bring up a small toolbar with icons to access EndNote.
While the methods for using Cite While You Write (CWYW) are similar, the details are different for Macs. This video highlights the differences.
This video goes through the steps for inserting citations into your document using CWYW in EndNote for Mac.
This video shows how to format the bibliography in EndNote for Mac.