Robots.txt in WM MWS

Hello,

Im sure this is will be fairly obvious, but have tried various locations and stuggling where to find to place the robots.txt file to prevent a googlebot regulary bringing up an error in our logs. Would anyone know of a way to confirm the location it should go in?

(Also, just joined for this question - apologies if posted in wrong place)

Cheers!
Mike

Your MWS is exposed to the Internet?