Automatically place grass using MinionsArt's grass

Right now I am trying to add grass to my terrain, problem is terrain is randomly generated so I am going to need to add grass automatically.

So far the grass code I found was this tutorial online https://www.patreon.com/posts/grass-geometry-2-40077798

I don't know how to make that into automatic grass, as so far I have to right-click to spawn the grass in.