Hey,
you don't rename the root user, in Unix systems a lot of software/services assume there is a user with this name and changing it will just break things. To get an idea of all the things you'd have to change in order to make it work, take a look at find /etc -type f -exec grep -l root {} +
. Generally you should just create a new user and give it the permissions it needs, this should be rather straight forward using the web UI.