When you have root-level access to a server, this means that you will have full control over it. That is to say, you can set up any server-side application no matter what the changes that it'll make to the software environment on the server, and you'll be able to both access and modify any file, which includes system files, and change any settings. You can do this by connecting to the server as a root user which has full privileges to do the aforementioned things and also to make other users, including users that also have full privileges. This connection can be established using a web-based graphical interface or a Secure Shell console. For safety reasons, it's recommended that you create a different user for your everyday work and employ the root user only when you need to modify the server or to set up software that may be needed by some script-driven application that you'd like to run.