Arduino Mega&Yun&XBee

Hi There

I have a project which is to transfer current data from a solar/wind LED light wirelessly. I'll use Xbee S2P to transfer data. Transmit unit will use Arduino Mega with XBee and the receive unit will use Arduino Yun to show data anywhere with XBee. The data of the solar/wind LED light is already recording in an SD card. So, just I need to transfer the data to the Yun.

Now, I don't know how I can transfer data between the two Arduinos. I don't know how i make the XBees talk. What codes I need to make them talk?.

Please I need a help from anyone, just the steps to start the project.