http://www.forgottenempires.net/install

Requirements
Age of Empires II: Forgotten Empires is an unofficial expansion for Age of Empires II: The Conquerors. You thus need the original Age of Empires II “Age of Kings” and the official expansion pack “The Conquerors” before you can install Forgotten Empires.
Install
1. Make sure to have Age of Empires II: The Conquerors installed
2. Download the installer exe | zip
3. Unzip the file into your Age of Empires II Installation folder (typically C:\Program Files\Microsoft Games\Age of Empires II\) (example picture)
4. Select your language
5. Click Install 

AoFE_Setup_Preview
Got problems? Check our Support page here!
If you have problems picking your language, check this page!
If you’d have troubles with the installer for some reason: Manual installation
Manual Installation Instructions
1. Make sure to have Age of Empires II: The Conquerors installed
2. Download the Manual installation
3. Unzip the file into your Age of Empires II Installation folder (typically C:\Program Files\Microsoft Games\Age of Empires II\)
4. Go to the /age2_x1 subfolder and run Fixaofe.exe
5. Run age2_x2.exe to play!
Enjoy!