Please help me with...............

my monogrammed cake topper with crystals on them

I ordered letters and '&' from www.topthecake.com
and now...........I am lost as on how to put crystals on them. I am sooooooo confused

I do not know where to start...How do I know what size of crystals to buy?? I have no idea what glue to use? Do you put glue on the crystals or on the letters??

I know my questions might sound stupid, but I am sooooooooo not crafty, but I still want to have a beautiful monogram cake topper for my cake Please help