If you have Base, without steering wheel control, then you need to buy the control tabs to replace your existing. Then run wires from clock spring steering wheel (plug E10), this is black plug (with 12 pins total), 3 wires:
EAU (Pin 4), AU2 (Pin 5), and AU1 (Pin 6).
Then those wires go to blue plug (E92, 20 pins) behind stereo. EAU to SWG (pin 6), AU1 to SW1 (pin 7), and AU2 to SW2 (pin 8).
I used internal CD-ROM/DVD-ROM computer audio plug that goes inside motherboard, it has 3 wires (red/white/black). Those female pins from CD-ROM perfectly match male pins in E10/E92. Pull those female pins out from the black plug then insert them to E10, I extended those wires so it can reach E92 behind stereo, then I pushed them inside E92. (See above mapping, remember the pin numbering sequence is when the plug is facing you, not from the back).
I got Volume +/-, Track +/-, Mode, Bluetooth pick up/down, mute, display. All working.
I have a Sport that has the audio and bluetooth controls on the steering wheel from the factory. I've been looking for an harness adaptor that would allow me to retain the call controls on the right side of the steering wheel. So far the only ones I've found just retain the radio controls on the left side.