Help with Alpha texture for my game?

So I have built this terrible tree, and I have a problem with the alpha texturing. This happens to me all the time and all of the tutorials I have seen tell me to do this same exact thing. When I use add in texture face the leaves are now partiallly transparent when I don’t want them to be and the background isn’t fully transparent. The picture explains it better.

Go and select alpha rather than add

also the image has to support alpha transparency for the alpha to work .png or .tga

Here is the file can someone see if they could get it to work? I tried alpha but that still didn’t work.
TREE.blend (424 KB)