To keep a folder to certain people, open Settings, then Permissions. By default everyone who can sign in sees the whole shed. A rule narrows one folder and everything inside it. Admins always see everything.
Find the folder in the list and choose Only these people. Put one email or domain on each line. A line such as @example.com lets in everyone at that domain. Save, and the rule applies at once.
Use Narrow a sub-folder and type the path as it appears in the breadcrumbs, such as Marketing Archives/Finance. A rule on a folder inside another wins over the one above it, so you can open a whole library to everyone and keep one folder in it to three people.
Browsing, search, downloads and ZIPs alike. Someone not on the list does not see the folder's name either: it is absent rather than refused. Shared links follow the same rules, so a link stops showing anything the person who made it can no longer see.
A rule says where someone can go. Their level says what they can do when they get there. Both apply: a person at Download level who is not on a folder's list cannot see that folder at all. See Invite someone and choose what they can do.
Every change here is recorded in Activity with who made it. What the shed costs is on Understand your invoice.
Tell us which libraries or drives are full and roughly how large they are. We size a shed, set up the first sweep with you, and most are running within a week.
Ask for a shed