First it has to be loaded or called the command before...
Call the command ARX
Enter an option [?/Load/Unload/Commands/Options]: C
Command Group 'ACAD_PUBLISH'
+PUBLISH, +PUBLISH
-PUBLISH, -PUBLISH
3DDWF, 3DDWF
3DDWFPUBLISH, 3DDWFPUBLISH
PUBLISH, PUBLISH
And use the command group prefix... like:
acad_publish.publish
HTH