How to use a prefab as a terrain?

I made a low poly terrain for my game with blender, i turned it into a unity asset, i placed it in the scene and, in order to use it, i added a terrain component to it, but i don’t know how to fill the terrain data box, what i need to do?97944-cattura.png

Terrain is not just a mesh but an intelligent GameObject which draws tris dynamically according to distance, a good way to import your lowpoly terrain would be to make a heightmap out of it, then import that onto an existing terrain