I can't place my Trerrains anywhere

I just made a new terrain for a game I am making but it won’t let me place it anywhere tell me am I just missing something rught unger my nose?

Oops “right under my nose?”

Hard to say what you missed without more details of what you did or the tileset file where we can see the terrain info you set up.

Did you follow the manual about Using the Terrain Tool?