Editing a terrain

I created a sample terrain last week to learn about how to create terrains. Today I went in to edit the terrain since I have read more about it, and it will not let me edit it at all. I would rather not start from scratch to create a new terrain. Also, if working in a project that needs to have a terrain edited because if client feedback, etc., how can I do that? Is there some secret to editing a terrain you previously created? It makes no sense to not allow you to edit a terrain, especially one that you created. If anyone could give me some help on how to do this, it would be greatly appreciated. Thanks in advance for any help.

Read this page in the Unity manual to learn how to create all sorts of terrain in Unity.

Thanks. I started over with a new terrain and it lets me edit it after reopening it. I think maybe the one I had been working on somehow became corrupt because it would not recognize the editing tool at all.

There's nothing special...select the terrain first. Then you can edit it.