To place baby inside the T-shirt:

Rest baby onto your shoulder. Slide baby’s opposite leg inside the cross panel and extend baby’s foot to the other side of the panel.
Pull the panel's fabric up, and stretch it so it covers baby's bottom and back all the way to below the knees. Pivot baby to the other shoulder and repeat these steps. BABY MUST BE WELL SEATED AT THE BOTTOM OF THE “X”.

Readjust the side panels then lift the bandeau over them, making sure the knees are well bent, and that the feet are resting in the bandeau’s fabric. Slide baby's head into a natural position into the neckline's fold (facing) without burying baby's nose.