sudo nano /etc/hostname
type your password
replace 'lisa-pc' with the name you want, then press 'ctrl+x' and hit enter to save the file
I am not sure if you will have to reconfigure your wireless connection by doing this so perhaps before you do any changes somebody here with more experience can advice.
By the way you need to back up all the important files before you do any changes, just in case.
Also you can tranfer the files from the /home/lisa folder to /home/tsali folder