APM 2.8 GPS Wiring

The wires are too short to plug into the GPS port and the I2C ,is the port on the side below the GPS port the same as the I2C or do I need to seperate the wiring so I can use the I2C port. I dont think the compass is working properly. It will hold position fine and hold altitude good but It will not RTL. It takes off away from me when RTL is applyed