psyduck,
write access: the administrator can control access to the i-bay by associating the i-bay with a group. All groups previously created in the groups section of the server manager will appear in the drop-down menu under "group" in this section. In addition, two default groups will always appear - "administrator" and "everyone" (meaning all users, whether on the local network or on the Internet).
"C" SME CAN DO...
Note: The hierarchy of ownership distribution in Linux features GROUPS (of users) and
the above excerpt of what you already did read (?) clearly describes "how to do" it:
= make an i-bay
"my-ibay"
owned by group
"mine" ( see write-acces via panel "Information Bays")

and user
"you" (or is it "me" )is (maybe the only) member of group
"mine"
Regards
Reinhold
PS: To get the basics behind this straigh, you might, from the commandline of your server, type
man chown and you will read much more.