This set of video guides by Dunkelschwamm is designed to teach you how to create maps in the editor WDC, and import them into your ECWolf or LZWolf project using SLADE.
By the end of this series you will be have a functioning custom mapset for Wolfenstein 3D, complete with custom episode names!
Other mapping utilities which you may find use in are Chaos Edit and Havoc's Wolf3d Editor. There are others, too, such as Eisenedit, WADE, and Mapcaster under development which all look very promising.
Congrats on completing PART 1 on your journey to mapping success! If that process of creating the WAD files seemed a bit tedious, fear not! WDC has a feature for exporting maps as WAD files with little difficulty!
You know how to make a single-map mod for ECWolf, but what about entire episodes? Wolf3d had 6 episodes with 10 levels apiece, so surely you too want the power to craft campaigns spanning multiple maps! If so, this is the tutorial for you!