How to add a external header lib to a VS2015 Project

[TaylorSasser]

I generated a lib of all the functions inside of a game by using DLL injection. The next step in my project is to incorporate the generated SDK into my own DLL and inject that into the games process allowing me to do various things. For some reason, when I add the headers it won't compile properly. This is what happens when I build into a DLL. There are about 18000 error lines, all with different methods.

RocketBot.obj : error LNK2005: "public: void __thiscall APlayerController::BugIt(struct FString)" (?BugIt@APlayerController@@QAEXUFString@@@Z) already defined in dllmain.obj


I am almost certain I am forgetting some small thing or making some rookie mistake.

https://gyazo.com/ad9618382c2b0d80bcde316fee944b24

DLLMAIN Code

#pragma once
#include <sdkddkver.h>
#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include <stdio.h>
#include <TlHelp32.h>
#include <iostream>
#include <synchapi.h>
#include <assert.h>
#include "RocketBot.h"

BOOL APIENTRY DllMain(HMODULE hModule,DWORD ul_reason_for_call,LPVOID lpReserved) {
switch (ul_reason_for_call) {
case DLL_PROCESS_ATTACH:
UGameEngine Test;
return TRUE;
}
}
RocketBot.h

#pragma once
#include "RocketLeagueHeaders.h"

class RocketBot {
public:
RocketBot();
~RocketBot();
};
RocketBot.cpp

#include "RocketBot.h"

RocketBot::RocketBot() {}
RocketBot::~RocketBot(){}


Here is a link to the SDK that contains the RocketLeagueHeaders.h on github.

https://github.com/TaylorSasser/RocketLeagueSDK

Lastly, if I made something unclear please let me know so I can fix it.