First C++ program can't compile - Unsure where to put third party lib

I'm designing my first C++ program but I'm having a hard time understanding how to install and use a third party library called pugixml.

Here is my structure:

• root/Makefile


• root/src/main.cpp


• root/include/pugi/pugixml.hpp


• root/include/pugi/pugixml.cpp


• root/include/pugi/pugiconfig.hpp

I believe I was meant to dump all the pugixml in a folder called pug in my includes folder and then refer to it from my Makefile like this;

CC = g++
CFLAGS = -g -Wall -std=c++11
SRC = src
INCLUDES = include
TARGET = main

all: $(TARGET)

$(TARGET): $(SRC)/$(TARGET).cpp pugi/pugixml.cpp
    $(CC) $(CFLAGS) -I $(INCLUDES) -o $@ $^ 

clean:
    $(RM) $(TARGET)

However when I run the Makefile or get this error:

main in main-bf0b72.o
  "pugi::xml_node::children(char const*) const", referenced from:
      _main in main-bf0b72.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [main] Error 1

This I've been told is due to thee fact that I have put the pugi cpp file in includes.

Question

• Where should the various pugi files go, if not where I have put them?


• How should I modify my Makefile accordingly?