When the Color Picker windows shows up, click on Custom. This will open another window called Custom Colors. In the drop down menu Book you can choose which set of colors to use. In this case choose PANTONE solid coated. Choose Pantone Orange 021 C and press OK. Photoshop will go back to the New Spot Channel window. You will notice that the name of your spot channel has become PANTONE Orange 021 C, whereas before it was simply named with a generic "New Spot Channel." Press OK.
The colors of your image might change again. Once again, don't worry about it, yet. Now go back to your Channels palette. Click on the eye next to the spot channel which you have just created in order to hide it. Click on the CMYK thumbnail on top of the Channels palette so you see all of your colors as they were before. Select the orange star. Make the spot channel visible again and hide the CMYK channels. Your image will be black and white to indicate that you are only working on one channel.
