Necessary materials checklist:
- ECWolf for your particular system: http://maniacsvault.net/ecwolf/
- Alternative, you can do all of this with LZWolf: http://wolf3d.net/lzwolf/
The base game:
- Wolfenstein 3D (If the mod is a Wolf3d-based mod) https://store.steampowered.com/app/22...
- Spear of Destiny (If the mod is a SoD-based mod) https://store.steampowered.com/app/90...
- OR Both at GoG: https://www.gog.com/game/wolfenstein_...
The map editor:
- WDC by Adam Biser: https://adambiser.itch.io/wdc
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.
The PK3/wad editor:
- SLADE: https://slade.mancubus.net/