When you import the material only contains a texture.
you need to actually create a proper foliage material and add the relevant textures.
its complicated, you should take the materials master class within the academy to learn.
In a gist. The image needs an alpha map, the material has to be set to foliage, two sided needs to be checked, and the alpha needs to be plugged into the alpha map.
you also need to inject a color into the sub surface. That’s the color leaves take when the sun shines behind them.