[LVL ED] Noob alert! How do I get the level editor?

[Your Computer]

I followed the direction very carefully, and I think I did everything right. Now when I try to run the application named "LevelEditor" a system error pops up and says that the SDL.dll is missing from my computer. This obviously a problem with my computer, and not the program or the process. How do I fix this?

Unless you're truly missing the file, then it sounds like you didn't extract it at the right location. You sure you extracted the HPL Editor Suite at Steam\steamapps\common\amnesia the dark descent?