Terrain scaling

Hi I'm kinda new to unity, and I've acquired an asset pack with trees and plats but wanted to use the terrain feature to simplify my map design. The problem is that the random height feature doesn't work, and I can't seem to scale any of the assets used. Does anybody know a possible solution?

 

You're going to need to be more detailed than that. "Doesn't work" could mean a huge number of different things that would all have different solutions.

What have you tried? What were the results? What are the results you're trying to get?

I'm not asking this to be a pain. We can't help if we don't have useful information.