The level editor is open when a lvl or lvlx file is active. The world editor is open when a wld file is active. You can make a new level or world file through the "File -> New" menu option.
If you appear in a black screen after starting a test (F5), that usually means that you forgot to place a start position.
Please do not use any of my assets (graphics, scripts) in works affiliated with the Novaverse. This applies to the original releases of those assets as well as any third-party variations (recolours, script alterations). Thank you.
The ABC of Creation