When you have root-level access to a server, it indicates 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 will make to the software environment on the server, and you will be able to both access and change any file, which includes system files, and change any settings. This can be done by connecting to the server as a root user who has full privileges to do the aforementioned things and also to create other users, including users who also have full privileges. This connection can be established through a web-based graphical interface or a Secure Shell console. For safety reasons, it's recommended that you make 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 which may be needed by a script-driven app that you would like to run.