Everybody knows how to do this by now!!

BUT.. In case you don't here's how...

Copy the Patch file into your Doom Directory
and enter the following at the command prompt :

DOOM -FILE MARKMU11.WAD

Once Doom Starts play episode 2 and get ready
to hear some cool music!  This will NOT alter
your Doom.WAD, don't worry!

You can also use this patch in conjunction with 
something else, a level for example.
