Broca's area is typically located in the left lobe.

The Broca's area is located in the lower portion of the left frontal lobe involved in speech and control the language expression. It is usually in the left hemisphere of the brain. This was derived from Pierre Paul Broca to examine patients on dealing with people having speech impairment.

If it's a smaller child or infant, place one on the middle of the chest and on the child's back. (if it is a bigger child with enough room for two, place one on the upper right/your left of the chest, and one on the lower left/your right) the pads should never touch each other.