Download the default program from the Innovation First site and edit it to output p1_y and p2_y to two more PWMs. So if you hook up your other two motors to PWM3 and PWM4, your serout command would be:
PHP Code:
Serout USERCPU, OUTBAUD, [255,255,p1_y,relayA,p2_y,relayB,p1_y,p2_y,p1_x,p2_x,p3_x,p4_x,p1_wheel,p2_wheel,p3_wheel,p4_wheel,127,127,127,127]