So how do I wire my rheem rgac-08ea so that my fan run independent

Dude, your question is way too vague... what are you trying to accomplish?

If your furnace is a heating only unit and you only have two wires going to the thermostat, it is not posible to turn on the fan only without doing some wiring.
So if you will tell me what you have I can tell you how to do what you are wanting to do.