Go to Options > Restrict Access to grant permissions on pages.
Page permissions are privileges granted to specified users and groups on a page. Page permissions that can be assigned are the same as the roles that can be assigned to a Pro Member.
Although individual users can be granted permissions on pages, we recommend you grant permissions to groups only (even if the group contains only one user). If a user's permissions need to change in the future, changes can be managed in the Control Panel through group changes rather than manual updates to individual pages.
When to grant page permissions
Semi-Private, Semi-Public, or Private pages need page-level permissions assigned for users or groups to contribute to content.