Hmm, looks completely different here, but this install is still 10.10. Never mind...
On 10.10 you can change the host name in the Network setting on the general tab, as I remember.
My hometown on the Mississippi River.
Using a Asus 3632QM laptop with 8gig RAM, 750gig Hybrid.
Machine Registered 366271, 366273, 366275.
Registered Ubuntu user number 18630. Registered Linux user number 458093.