How can I place objects in specific places on randomly generated terrain?
Sort of like a biome.
You can try to look in the unity script API and under INSTANTIATE Unity - Manual: Instantiating Prefabs at run time
Becouse is sounds like you have made the random terrain and just wants the Gameobjects to be spawned if i follow you ?
If height is the only issue, you can use Terrain.SampleHeight() to place the object at the correct height. If you need both the height and the slope, you can Raycast() down on the terrain using a form of Raycast that takes a RaycastHit struct. From the struct you will get the position of the hit (point), and the slope (normal). You can use both to place and rotate your object to match the terrain.