I have 5 wires total. The red, green and white are extending from the wall in a singel wire casing. The I have a red and a white in a separate wire casing. How do I know which red wire goes where and which white wire should be considered the yellow wire?

Go to the furnace and take the front covers off. You will see where the thermostat wires are connected. Let me know where each wire is hooked in the furnace and I will try to help you out. This will be the only way to know for sure where to hook the wires at the stat.