I know how to place terrain, but when I do it is not showing up, what am I doing wrong?
Select your terrain in the Hierarchy panel, then hover your mouse over the Scene View and press the F key. That should focus the scene view on your terrain. It might also be a case of your scene view camera being below the terrain, which will make the terrain invisible to you, so you need to pan and rotate your scene view until you get the right angle to see your terrain.
thanks, but the only way I can see it if I am underneath it D:
That means your scene is entirely turned upside down. In the top right corner of the Scene view there is a gizmo. The Y axis of that gizmo is probably pointing down. Rotate your scene view in a way that Y will point upwards. You will then see your terrain while on top of it (since you effectively take what you see right now and turn everything upside down :-))