DOSBox is a full MS-DOS emulator, not a WAD interpreter. Get a shareware version of Doom elsewhere, complete with the executables, then read any of MiniMax guides about how to run games.

Yeah but I'm on a Mac so there's really no other way to run "Doom". Are you sure there's no way to get the program to read a different WAD other than the DOOM1.WAD file?

yup download shareware doom from here: http://youfailit.net/pub/idgames/historic/

You don't seem to understand. DOSBox will run whatever version of "Doom" you own, either shareware or registered, as far as you also have all their files, not only the WADs.

If you only have the WADs, you'd better try Doomsday Engine, it's got a MacOS version.

I don't think my question was clear enough. I HAVE the shareware version of Doom and it runs fine using dosbox on my mac. However, I want to play a Doom WAD other than Doom1.WAD that comes with the game. How would I play a different wad using the shareware version of doom on dosbox?

you need the full version of doom to run any Pwads. (add-ons) or try with freedoom.

The command line would be Doom.exe -file name.wad.