If you have root-level access to a server, it indicates that you'll have full control of it. That is to say, you'll be able install any server-side app irrespective of the changes that it'll make to the software environment on your server, and you'll be able to both access and modify any file, which includes system files, and modify various settings. This can be done by connecting to the server as a root user who has full privileges to perform the aforementioned things as well as to create other users, which includes users who also have full privileges. This connection can be established through a web-based graphical interface or a Secure Shell console. For security reasons, it is recommended that you create a separate user for your everyday work and use the root user only when you have to modify the server or to set up software that may be required by some script-driven app that you'd like to run.