MSDOS is no longer included on Windows, but there are multiple free ports and emulators that allow you to play the game in modern systems.
DosBox is a program that emulates MSDOS, and the best way to go if you want to play the original version of Wolf3D. This is also the optimal way to play many classic mods built on DOS or the DOS4GW engines.
An open-source project by community member Ripper, this is the original source port that lets you play the game on modern Windows systems without emulation, and is also the engine of choice for bigger and more ambitious modding projects.
Forum thread.
This is an “advanced source port” for the game, built off of Wolf4SDL. It can run on multiple platforms (including Android), and supports many modern changes like WSAD controls.
It is still in development, with support for more games and more deep modding options in the pipeline.
There are other ports over the years, including NewWolf (Which lets you play in OpenGL with 3D graphics if you want), and Wolf3DRedux, but most of those projects have been on indefinite hiatus though, and mainly act as artifacts of history.
Each of the above options will run the original game, but you have to own the appropriate game files first. Find out where to get Wolfenstein 3D here.