I'd start them out between 6" and 8" away from your plant - then monitor carefully to adjust! Since it's probably a pretty weak light for our kind of grow, it may not do much but as I said, it'll be better than nothing. The main concern I would have is how much heat it puts out... You could plug it in away from your plants and test the amount of heat (just feel with your hand)... figure out how far away from the light your HAND is comfortable and start there..
Best of luck!