Step 1 is to download ECWolf. Below is the link from where you can download the .zip file. You will need WinRAR or 7-Zip to unzip the files.

https://maniacsvault.net/ecwolf/download.php

After downloading, unzip the files.

Right-click Wolfenstein 3D in your Steam library, then click Manage. In the drop-down, select Browse Local Files.

After that, go into the DOSBOX folder. Copy all the ECWolf contents you extracted previously and paste them in this current DOSBOX folder.

Delete the existing DOSBOX.exe file and rename ECWolf as DOSBOX. This way you should be able to launch it through Steam.

Launch the game from Steam atleast once.

After you have launched the game through Steam once, head over to your appdata roaming folder. Press Win+R and type in "%appdata%"

It should take you to the Roaming folder. Then open ECWolf folder. Edit the ecwolf.cfg file with Notepad.

Scroll down till you see "BaseDataPaths: <some gibberish>"

Copy and paste the below line to the BaseDataPaths string:

BaseDataPaths = ".;$PROGDIR;C:\\Users\\<your username>\\AppData\\Roaming\\ECWolf;\\AppData\\Roaming\\ECWolf;C:\\Program Files (x86)\\Steam\\steamapps\\common\\Wolfenstein 3D;C:\\Program Files (x86)\\Steam\\steamapps\\common\\Wolfenstein 3D\\base\\m1";

Make sure that in <your username> you put the username your computer is using. Save the file, and launch it through Steam. Now you should be able to choose Wolf3D or Spear of Destiny everytime you open the game. Make sure you don't click "Don't show this again".


(by MrHustler) If your game crashes after changing your Resolution go back into the ecwolf.cfg file with notepad and look for >

FullScreenWidth = 640;
FullScreenHeight = 480;
WindowedScreenWidth = 640;
WindowedScreenHeight = 480;

Change it to your Resolution >

FullScreenWidth = 2560;
FullScreenHeight = 1440;
WindowedScreenWidth = 2560;
WindowedScreenHeight = 1440;