To edit the file /etc/hostname, enter:
$ sudo vi /etc/hostname
Delete the existing name and replace it with a new name:
fedora28-ucartz
Save and close the file. You may also need to edit the /etc/hosts file, enter:
$ sudo vi /etc/hosts
How to set the hostname on Fedora Linux
With the latest version of Fedora Linux that uses systemd, it is possible to use a single command as follows:
# hostnamectl set-hostname {NameHere}
# hostnamectl set-hostname fedora28-ucartz