Hi, I had the same problem - but eventually found this - If you look at the bars going across the front,under the second one down in each corner is a screw. They are small philips screws - painted black. Undo them and pull the front away. Make sure you take all the coal bits off first! You will need one/two narrow thread screw in 40w candle bulb.
Cheers!
IANB, November 2006