When you have root-level access to a server, this means that you will have full control of it. That is to say, you'll be able install any server-side application irrespective of the changes that it'll make to the software setting on your server, and you are able to both access and update any file, including system files, and modify any settings. You can do this by connecting to the server as a root user which has full privileges to do the aforementioned things as well as to create other users, which includes users that also have full privileges. The connection can be established through a web-based graphical interface or a Secure Shell console. For safety reasons, it's recommended that you make another user for your everyday work and employ the root user only when you need to modify the server or to set up software which may be needed by a script-driven app that you wish to run.