Question Import FBX model into Unity : alpha/opacity map texture doesn't working

Hello,

I'm likely a "newbie" into Unity and i'm creating a little 3D game (more like a digital activity than a "game" actually). i have download a 3D model (fbx file with all texture map) into the software, but the alpa/opcaity map is seems not working : the texture image is fully taken. The file i have download is a tree, and the leafs are created by .png texture and for this example, when i add the tree in my scene, le leafs are simply square format. How can I fix it pls ?
(sorry for my bad english)