To attach a Maxi-Cosi infant car seat to the Agio Z4 or Peg-Perego YPSI, you will need to purchase these Agio Z4 car seat adapters, which are sold separately from the stroller. The car seat adapters are a set of two small posts with a glossy button at the front of each used to detach the adapter from the stroller. If using your Z4 or YPSI stroller as a double for twins you will need to purchase two of these adapters, as well as the Z4 / YPSI Double Adapters, to attach two Maxi-Cosi car seats at once.
To attach the car seat to your stroller, remove the stroller seat if its on the stroller and place the adapters on either side, with the glossy adapter button facing the front wheels. You will then lower your Maxi-Cosi infant car seat onto the adapters until you hear the adapters click into place, with baby facing the handle of the stroller.
To remove the car seat from the stroller, you will press the small grey buttons on either side of the Maxi-Cosi car seat, located on the car seat near the canopy and where the handle rotates. While pressing down on these buttons, lift up on the car seat to remove from the stroller! You may find it easier to release one side of the car seat at a time while lifting up on the car seat handle. The adapters can stay on the stroller, but should be removed before attaching a bassinet or the stroller seat; just press the glossy buttons on each adapter and lift up to remove from the frame.