Restoring Macbook after Maverick

I went the Apple store and recieved help at the Genius Bar. They started my computer fresh with Maverick and all I had to do when I got home was choose to download from an earlier backup. When I did that I chose the wrong HD on my Time Machine and now I don't know how to fix it. How do I now choose the most current update from my external hard drive? Please help. TIA