Add necessary information to README

Author: DaZombieKiller

README.md

@@ -1,2 +1,40 @@
-# PluginManager
-Unity Plugin Manager
+# Unity Plugin Manager
+## Introduction
+Unity Plugin Manager (herein, UPM) is a tool for creating plugins and mods for games developed with the Unity engine.
+
+## How it works
+UPM injects a static constructor into the GameObject class found within UnityEngine.dll. This way, it is able to execute code before anything else in the game. Using this, it loads plugins from a folder named "Plugins" in the game's folder, and instantiates any MonoBehaviour derivatives with the [OnGameInit] attribute.
+
+## Building
+In order to build, you will need a copy of UnityEngine.dll  
+This file can be found in the _Managed_ folder of any Unity game, or within Unity itself.
+
+If you don't have a built Unity game on-hand, you can retrieve UnityEngine.dll from the following location:
+
+(Unity Install Folder)/Editor/Data/Managed/UnityEngine.dll
+
+After obtaining this file, place it in the _Managed_ folder present with the UPM source code. Then, if on Windows, execute `generate.bat` to create project files.
+
+If not on Windows, follow the Protobuild project generation instructions for your platform.
+
+From here, building UPM should be as simple as compiling the generated solution file in your C# IDE of choice.
+
+## Usage
+After building UPM, you should have the following files (present in _Source/(Project Name)/.../bin_)
+
+* PluginManager.Installer.exe
+* PluginManager.dll
+* Mono.Cecil.dll
+
+Any other files are not necessary for usage of UPM.
+
+Place the aforementioned files into the directory where your target game is located, and run `PluginManager.Installer.exe` (using Mono to do so, if not on Windows)
+
+If UPM installed successfully, you should see a message stating `Plugin manager installed.`
+
+Running the UPM installer again will uninstall UPM from the game.
+
+You are now free to create a `Plugins` directory and place your plugins in there.
+
+## Creating plugins
+Refer to the [sample plugin](https://github.com/UnityPluginManager/SamplePlugin) as an example of how to set up a project. Essentially, you must create a .NET 3.5 library project that references UnityEngine, PluginManager (UPM) and any other assemblies you may require from your target game. The sample project can be used as a starting point (see the repository for more information).