A simple one liner here to update the hostname (computer name of Mint Linux 18).
I had to find out the name of the text editor installed. I typed, "text" in the launch bar, opened the text editor, selected: help, about. This told me the name was 'xed'
So open a terminal window and type
Sudo xed /etc/hosts
Which will open an administrative text editor.
Simply replace the host name with what you want, save and reboot.
Another method is simply to type sudo hostname - but that only TEMPORARILY changes your host name!
The method I mentioned first will do it permanently!