In Chapter 13, readers are instructed to copy the Add icon image, and the book explains where to find the icons:
System icons can be found in your Android SDK directory. On a Mac, this is typically /Users/user/Library/Android/sdk. On Windows, the default location is \Users\user\sdk. You can also verify your SDK location by opening the project structure window and selecting the SDK Location option.
On my PC, however, it was installed by default to C:\Users\John\AppData\Local\Android\sdk,
I also forgot about the Project Structure window and had to google it to jog my memory. It can be found under File > Project Structure.
Hopefully this helps other readers who may have been confused by this section.