Hi
EasyBCD it pretty, well, easy.
if you have two viable operating systems on your computer it should see both of them and let you add the one that is't showing to your Boot.
I can't tell you step by step because it's been so long since I've done it but it wasn't difficult.
I think you can navigate to the .exe file for the OS you want to add and just select it, through the Add New Entry tab.
Take a look at it, and then if you need help come back with a specific question about the process and some one will be able to help you.
Mike