In order to secure the SQL access, you will need to create new users for operating with your LeanXcale database.
In Cloud Console interface, users can be created under the SQL Interface Security section, where you’ll also see the previously created users.
If you want to create new users, click on the "Add User" button and fill the User and Password fields, then click the "Save user" button:
If you are managing a LeanXcale installation outside a Cloud environment, you will need to use the admin console (you can learn more about admin console here).
The tool to use is  addUser [username password database]. You have to provide a name for your user, a password and the database name (at the moment, you must always use 'db').