I have my Arduino Uno and Arduino A000079 Motor Shield, R3, 5V to 12V working but trying to use tutorial code for DCC++ and it needs the correct $INCLUDE library added. I tried several libraries but none seem to work all that well.
First, it's #include, not $INCLUDE.
Second, the shield you are using came with a library. THAT is the library you should be using, and whose header file you should be using.
First of all, welcome to the Forum. Secondly, can we see how you've wired everything (circuit diagram)?
And on and on. Let's have a look at the code you're using (posted neatly inside code tags, see instructions at top of Forum). Lastly, when the time comes, it will be #include, not $INCLUDE.
PaulS:
Second, the shield you are using came with a library. THAT is the library you should be using, and whose header file you should be using.
Are you sure? I just looked at the official documentation and found no pointer to a library.
https://store.arduino.cc/usa/arduino-motor-shield-rev3
For support, they point to the forum. 
Further searching turns up no library specifically for this board for controlling DC motors. Some recommend using the library for the Adafruit motor control board. It looks like another fair choice might be the "Motor Driver Library" by CuriosityGym, available through the Library Manager (Sketch->Include Library->Manage Libraries...).
Are you sure? I just looked at the official documentation and found no pointer to a library.
No. Somehow I misread that as an Adafruit product.
I'm not sure why anyone needs a library to turn the direction pins on or off, or to set the PWM value of the speed pins.
enpiccoli:
trying to use tutorial code for DCC++ and it needs the correct $INCLUDE library added.
Can you point to the tutorial code you are trying to use?