When you have root-level access to a server, this means that you'll have full control of it. In other words, you can install any server-side app whatever the changes that it'll make to the software environment on your server, and you will be able to both access and customize 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 all these things as well as to make other users, which includes users that also have full privileges. This connection can be established using a web-based graphical interface or a Secure Shell console. For security reasons, it is recommended that you create another user for your daily work and employ the root user only when you have to modify the server or to install software which may be needed by a script-driven app that you'd like to run.