If you have root-level access to a hosting server, this means that you'll have full control over it. In other words, you can install any server-side app no matter what the changes that it'll make to the software environment on the server, and you are able to both access and update any file, which includes system files, and change various settings. You can do this by connecting to the server as a root user who has full privileges to perform the aforementioned things and to make other users, which includes users who also have full privileges. This particular can be established with a web-based graphical interface or a Secure Shell console. For security reasons, it is recommended that you make one more user for your everyday work and use the root user only when you have to customize the server or to install software which may be required by a script-driven application that you wish to run.