The 3pi uses the same chip atmega168 as the arduino, but you need to program it with avrstudio. I would download that from atmel and go from there if you have the non arduino version of the chip(ie no boot loader on the chip).
If you are in fact using the arduino then you should read the documention as well as this page that pololu has put up on the page related to the 3pi that should help you further.
It works in arduino. i did everything the tutorial said, and now it says wrong microcontroller found.
Binary sketch size: 1124 bytes (of a 16384 byte maximum)
avrdude: Expected signature for ATMEGA168 is 1E 94 06 Double check chip, or use -F to override this check.
how do you fix this?