Assigning an IP Address to a Switch
From Peter Pap's Technowiki
1. Select the default VLAN interface
config t interface Vlan1
2. Assign an appropriate IP and enable the interface
ip address 192.168.X.X 255.255.255.0 no shutdown exit
3. Set the default gateway
ip default-gateway 192.168.X.X exit
NOTE: If ports are using a different VLAN, for instance VLAN5, then you will have to create new VLAN interface and assign the IP to it to make this work.