If it says something about wad file, then download doom wad file from here: https://www.pc-freak.net/blog/doom-1-doom-2-doom-3-game-wad-files-for-download-p... and put it in the folder with chocolate doom
If it says something about wad file, then download doom wad file from here: https://www.pc-freak.net/blog/doom-1-doom-2-doom-3-game-wad-files-for-download-p... and put it in the folder with chocolate doom