Texture with alpha, add colored texturemap to alpha?

Hi all. It’s my first post here. I will like to know how to do this stuff.
I have a texture that is AO add to color channel on my basic material exported from Maya. This texture have a alpha channel. Alpha channel is a Grey variation of intensity of my color map(AO). I will like to make a material where i can use the transparency of the alpha channel and add a colored map, like grass in my case. It is similar to assetto corsa KSEditor and material creation. I hope it’s clear.
Thanks