Can't look at the moment, but from the top of my head:
game files are in
/Applications/The Elder Scrolls Online
(append "EU" for, well, the EU client)

settings files and screen shots are in
/Users/<account name>/Documents/The Elder Scrolls Online

HTH

P.S.: If you meant how to get the game's installer for Mac, log into your account with Zenimax at https://account.elderscrollsonline.com/. If you have Early Access, the links for PC and Mac clients should be in the "Purchased Games" section.