How to share a calendar, folders, etc. in owncloud for a group of users or for a single user?

Question

Access rights

Good afternoon.
In Ovncloud, you can share folders and a calendar for users from an address book in the cloud. Instructed to start typing a group name or username and select from a list (live search). But no matter how hard I try, and no matter what names I come up with for groups and users, the result is the same - it does not find users and groups.
Please tell me, maybe I'm not sharing correctly, or what's the problem.
Thanks.