Trouble getting my heightmap in-game. HELP!

[Roadkill]

I'm new to map-making. I just finished my first heightmap with Gimp and I can't get it into the game. Whenever I type in the name, a box comes up that says "Cannot find maponeTerrain.png!" I've tried everything under the sun. EVen reinstalling the game. Nothing works... PLEASE HELP!

[Roadkill]

Nevermind! I figured it out. It was the wrong file type. XD