Because you are using, what I assume is, the EX2100 you may want to post your question to the dedicated EX Series subforum which covers the EX2100 and EX4100 series. This subforum (My Cloud) generally covers the single bay My Cloud units.
If the EX2100 series is anything like the single bay My Cloud then one should be able to configure per user access (full access, read only access, no access) through the My Cloud Dashboard. With the single bay My Cloud there is no easy way to prevent the users from seeing all the Shares/folders. They can only be prevented from accessing a Share (again on the single bay My Cloud).
If you haven’t done so already you should read through your My Cloud User Manual to understand its features and how to use/configure them. Or see the My Cloud Dashboard Help.