Managing users under settings? Normally one manages the My Cloud users via the WD My Cloud Dashboard under the User page. From that page one can manage which Private Shares that User can access. Here is an example of the User page from the My Cloud v4.x User Manual.
An image of what you are looking at and using would help.
I have two users on my My Cloud, my daughter and myself.
I have five shares, “Shares are content storage areas—like folders.”, this is quoted from the Dashboard under About Shares. They are, Public, Catherine, TimeMachineBackup, Horace and SmartWare.