How do you configure desktop for a static IP address?

Right click nm, choose Edit connections... find your interface, click Edit..., click IPv4 Settings, choose Manual and configure your interface.

An alternative would be to edit /etc/network/interfaces. an example configuration would be:

auto eth0
iface eth0 inet static
   address 192.168.1.1
    netmask 255.255.255.0
    gateway 192.168.1.1

then run

/etc/init.d/networking restart

Keep in mind that this will deactivate nm for this interface and you will have to delete (or uncomment) the entries to activate nm again.

Edit (see Casey's post): You also have to set a DNS after editing /etc/network/interfaces:

Set one or more desired nameserver in /etc/resolv.conf:

nameserver 192.168.1.1

Update /etc/networking/interfacesto set the static address:

auto eth0
iface eth0 inet static
    address 192.168.0.10
    netmask 255.255.255.0
    gateway 192.168.0.1

Set one or more desired nameserver in /etc/resolv.conf:

nameserver 192.168.0.1

You must prevent gnome-network-manager from attempting to hijack the eth0 connection:

sudo apt-get remove network-manager network-manager-gnome

Assign static IP address by restarting the networking sub-system:

sudo invoke-rc.d networking restart