Hi,
Normally in Atomic , you can put this option by typing it directly behing the Emulator name on the "folder " tab. Directly in the edit field.
ex , if you have :
c:\mame\mame.exe
you have just to add in the field behind :
C:\mame\mame -skip_disclaimer
or you can do that in the mame.ini of course.
But of course if your mame version doesn't support that option it will not work.