How to enable share access to public?

Just got the My cloud EX2 Ultra. I followed instructions to set up. Now I want to transfer filers to this external HD. But “Share Access” in the menu is grayed out.

Here are some articles that may help you:

http://learn.mycloud.com/
https://support-en.wd.com/app/answers/detail/a_id/9323/h/p2
https://support-en.wd.com/app/answers/detail/a_id/25436/h/p2