First of all, make sure you type the command correctly, letter to letter, and note that in linux small letters are NOT equal to capitals as often in windows. So, to edit the interface information you need to open the nano editor with:
Are you telling us it open a blank file? The fle should not be blank, you should see text already in it.
sudo nano /etc/network/interfaces
The section for the first wired interface by default would usually be like:
You need to replace it with something like (note that the information will depend on your LAN subnet, the gateway, DNS servers you want to use, etc):
iface eth0 inet dhcp
That is sort of a basic setup. Again, please note that the exact options you need to enter will depend on your LAN. Don't simply repeat the configuration since you might need modifications.
iface eth0 inet static
dns-nameservers x.x.x.x y.y.y.y
After you modify the file, save it with Ctrl+O, Enter. Then close it with Ctrl+X.
For the new config to be applied either restart the whole server or only the networking:
sudo service networking restart