In the Swatches panel menu button, you can choose a new color swatch. Set it as a spot color and pick a named color from one of the Pantone libraries. One way you can tell a swatch is a spot Pantone color is the little gray square icon has a round spot in it.
Open the Separations Preview panel (Window > Output > Separations Preview). Turn on separations. It will show which objects are on which printing plates.