You have to put the big bar through the wholes in the side attachments first before attaching the spring loaded bar. The big bar should be facing toward the front of the stroller.

Once the bars are all attached, the to clicky slots on the Peg should click into the small cross bar and the spring loaded bar. The big slot on near the back of the Peg should rest on the big bar.

I've done this and the car seat appears at an odd angle, but in general works and is stable. However, when I tried to attached the City Select seat in the bottom position, it does not appear to fit all that well with the Peg Perego Car Seat. Thoughts???