Put the sub-part 
"47398s01.dat"
into the "S" subdirectory of "parts" (path: LDraw/Parts/S). You also can put other unofficial parts into Ldraw's "models" directory for later usage. By putting unofficial elements in the "models"-directory you keep your official partslist "clean".

MLCad still might start complaining about missing files (primitives or whatever...) In case an element isn't displayed correctly, write down it's name, go to www.ldraw.org and get it from there. Make sure you save it to the right folder of MLCad! (eg. Primitives -> LDraw/Parts/p)
