The passenger side seat sensor automatically turns ON when a weight is placed on it.
You should never hold a new-born/child when sitting in the front passenger seat, due to potential airbag deployment. All children are required by law to be in a child or booster seat.
You cannot place a child or booster seat in the front passenger seat in front of an airbag. Illegal in most, if not all, states. Child and booster seats are for rear seats only. This is all described in the GC owner's manual (starting on page 83), including how to use the LATCH system in the rear seats for installing child or booster seats.