Rainbowduino over i2c

hello, purchased rainbowduino v3 (http://www.seeedstudio.com/depot/rainbowduino-led-driver-platform-atmega-328-p-371.html). constructed large 8x8 matrix of common annode rgb leds , wired them correctly rainbowduino. now, can connect rainbowduino computer via usb, write sketches, , work properly. goal add ir receiver , sd card (for storing ton of animations). i'm assuming can't somehow use pin headers on rainbowduino, guess need wire arduino uno r3 , transfer sd data on i2c. lost on how this. connected 5v , ground eachother, a4 sda , a5 scl, , guess @ on code:

code: [select]

#include <wire.h>


void setup()
{
 wire.begin();
}

void loop()
{
 wire.begintransmission(); // i2c address???
                             
 wire.write(rb.setpixelxy(0,0,255,255,255));            
 wire.endtransmission();    

}

this got command put in wire.write() (http://www.seeedstudio.com/wiki/rainbowduino_v3.0#using_with_rgb_led_matrix).
am on right track? info @ appreciated please keep in mind amateur @ arduino , programming, please explain things i'm 5 years old.

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