Actionscript macromedia 8 - stuck on sliding menu

I have used the sliding menu instructions from this site

but seem to be messing it up somewhere despite having done it 8 times now. When i unzip the files, it comes with B1-5, Content 1-5, em and em2, holder and maskMovie. I assume they are for me to use.

I think I am doing it all right up until the bit where I cover with a mask over content 1 which is held within the contentHold

Do I use the maskMovie or draw a box in myself?

When I test the movie, ie click on of the coloured buttons down the side, all that happens is the buttons disapear and I am left with a coloured strip down the side ie the colour box that I have just clicked.

Sooooooo confused!!!