For new users, here is the link to download it:
https://persistent.oaistatic.com/sidekick/public/ChatGPT_Desktop_public_latest.dmg. It is being rolled out to ChatGPT+ and free users over the next couple of weeks. ChatGPT Plus users have priority for getting access, so please be patient. If you do not have access, you cannot use the app.
It is only available for M series Macs, not Intel. There is no other official download.