Windows 64-bit doesn’t support DOS applications.
Windows 32-bit included NTVDM, to some extend facilitating DOS programs to run. PC’s now come with Windows 10 64-bit installed, mostly without an option to downgrade to Windows 32-bit. Starting a DOS program will display a popup it can’t run…
…Microsoft dropped 16-bit support (so also DOS) in all Windows 64-bit versions, not just recently with Windows 10!
To find a version for your PC, check with the software publisher.
That probably doesn’t help: The DOS application could be developed by yourself, a company not supporting it anymore, or out of business for years. Despite Windows versions/alternatives, you may prefer - even forced - using it for various reasons and time to come.

First option was to install a virtual Windows 32-bit system. The setup can be daunting, to 'only' run that DOS application, its use overkill and cumbersome. DOSBox is a popular alternative, but intended for gaming only.

vDos lets you conveniently run DOS applications by emulating a (spiced up) DOS PC in a window. vDos itself runs on Windows 32 and 64-bit systems, Windows 7 or later.

If you don't already use (still rely on) a DOS application, want to play/experiment with DOS, its command prompt, programs or games: Forget about vDos, it is not meant for you!

Don’t just hurry to the Download page. vDos may still not be what you’re looking for, external 'expert' reviews mostly don't actually get it. Frequent use of vDos may even cost you inconvenience or money, you don’t want to spent. First have a look at some other pages!
vDos highlights:
Start DOS applications instantaneously in a scalable window with a crisp TTF font (in text mode).
It focuses on serious programs, setup yours easily. No complex configuration to load drivers, set file handles, keyboard layout, language character set…
Run multiple DOS applications, if needed with their own specific configuration.
Print to Windows-only (GDI) printers, or a virtual printer to produce PDF’s.
Its file system is (in sync with) that of Windows, no internal disk caching corrupting files.
Network support with file- and record locking, required by multi-user DOS applications to function reliable.
Copy/paste text from Windows to DOS and vice versa, with transparent conversion of Windows/DOS text.
vDos by JHM Schaars - Zevenaar - The Netherlands - CoC registration 09103086