Question How to add alpha texture(black/white) to albedo texture for transparacy?

I am trying to make a leaf texture that is transparant.
I have an albedo texture that have leafs on it and the rest is just of green color and an opacity texture that is an alpha (black/white).
The textures are from megacans library and I use the standard shader.

On the albedo texture it says on the setting Alpha Source - Input Texture Alpha! , but where?! where do I set this texture? Why not just have have in input texture slot here for the alpha cut out?

I have set the Rendering Mode to Cutout.
Do I set the opacity(black/white alpha) texture on the matalic slot? and set source to Metallic Alpha?.

 

Why don't you use Adobe Photoshop or equivalent software to clean the green area first then save it as PNG and then import it with the option (alpha is transparent) and/or make it sprite 2d to see it transparent.

Here are tons of videos
https://www.google.com/search?q=photoshop+clean+green+background

 

Thank you for the answer but I have 100 of textures that I have to do this so it will take a long time. There must be an easier way?

 

Photoshop also has "actions" to automate the process