Depending on your platform this is done by assigning “Rights” or “Permissions”. These can be inherited from the folder above, or that inheritance can be denied. For individual users folders, I block all inheritance and then assign full rights to the user in question. On Windows servers you can see this info by right clicking on the folder, selecting properties, and then choosing the security tab. This is a basic function of a file server, and the permutations are vast. I suggest you read up. Note, you should know the password for your administrator level user on the server. This will always be able to see all folders.
Regards – Doug