The instructions you are referring to apply to the Debian reference image, not Fedora.
Fedora out of the box doesn't use sudo. In order to gain administrative privilages you would typically need to switch to the root user by issuing a command like "su" or "su root" and then enter the root user's password.
Given that you're new to Linux, I would suggest dropping the Fedora image in favour of the officially supported Debian image
which is up to date and in much wider use. It boots to the command line by default too
Because it's the more popular image of the bunch, you will naturally find a lot more documentation for it too.