Solarbotics documents this kit fairly well, so I won't bore you with all the step-by-step details. Here is the completed board prior to attaching it to the ATmega328.
Slide the ATmega328 between the pins of the Ardweeny board, making sure that the board pins are perfectly aligned with the ATmega pins. Do not slide the tips of the board pins any further than the wide tops of the ATmega chip pins.
Solarbotics warns not to let solder run down the pins of the ATmega328 when you solder-tack it to the pins of the Ardweeny board. This is critical so that the pins of the ATmega will fit correctly into your breadboard. You can see here that I flipped the entire unit upside down for soldering to help make sure this didn't happen. Boy, was I glad I did this! If you look closely at the full-sized picture, you'll see that some solder ran down the leftmost pin of the Ardweeny board. This is fine, as that portion will not be inserted into the breadboard, but it would have made for some difficult rework if it had run down the leg of the chip. Another tip that might help is to solder the four corner pins first to help ensure the chip does not shift position during soldering.
Here is a profile shot so that you can see the gap between the top of the ATmega chip and the bottom of the Ardweeny board. This is normal if you assemble them correctly. Oops! I didn't leave enough room on the breadboard for the h-drive chip! I'll have to move the Ardweeny.
Here is the breadboard with the three main components: the voltage regulator, the Ardweeny, and the H-drive chip. Time for refreshments!