Update the below file
`sudo nano /etc/network/interfaces`
to look like below
`auto eth0
iface eth0 inet dhcp`
Then finally do like below
`sudo /etc/init.d/networking restart`
To manually update your ip, do like below
`ifconfig eth0 192.168.1.5 netmask 255.255.255.0 up`
I connected my pi to a Mac book pro via LAN. The Mac book was set to share its internet connection. Make sure the thunderbird is green on the Network setings.
Then you can do like below to install xfce desktop
`
sudo install_xfce_desktop`