File ownership

when I try to configure Wvdial following this page http://support.real-time.com/linux/dialup/wvdial.html recommendations and try to modify the wvdial.conf file, I'm denied the right to do so because I don't have ownership to the file.
What should I do in order to take ownership,modify the file and save it to be able to dial up from console

From the instructions on that pageIn a terminal if you see a prompt that looks like this
mingdao@lappy:~$
with a $ sign, that means you're logged in as a normal user.
Issue "su" without the quotes, switch user, and if you only
have two users on your system it will prompt you for the root
password. When you're logged in as root, it will look like this
root@lappy:/home/mingdao#
with a # to indicate root is logged in.

Don't run your system as root. This is your first line of defense
as far as security is concerned on a Linux system. Run as the
normal user.

You can also issue su -c and the -c tells it to execute the command
that follows su. For instance, to edit the file, if it is named wvdialconf
you would issue it like this
mingdao@lappy:~/wvdial-1.54.0$ su -c "pico wvdialconf"
password:
and when you enter your password, it would switch users to root,
allow you to edit the file, and when you save the file it will return
you to a normal user. NB: The quotes are needed in this last example.