Microchip supplies a wealth of libraries, including ones to use I2C. They are all present in a full install for the CubeSat Kit. I can guarantee you that it will be very difficult to get I2C up and running unless you have some sort of I2C protocol analyzer ... we sell the Total Phase Beagle one, that interfaces directly to a CubeSat Kit via the CSK Breakout Module.
In terms of connecting an I2C periperal to the CSK, you do it over SCL_SYS and SDA_SYS, and you will have to decide on the pull-up voltage (either on the CSK Dev Board or on the Arduino).
Hey, I am trying to Interface Cubesatkit PIC with Arduino UNO. I am using an I2C interface but could not make it. Can i use the SPI or UART for communication. Is it posible to communicate without I2C protocol Analyzer when we use SPI. Is there any other means for communication. If so please help me.