How to connect two LAN networks using only one network device the switch?

hey guys

please help me this!

we are designated to have a network connecting two LAN using only one switch or hub..
how will i connect this two LAN using only one switch?please help me guys….i really need your help….

we will be given one NIC card aside on the on-board lan card…what will i do then?i really need your help…please..help me as soon as possible…