Shampooer instructions.....

Question

I have a Kirby Generation 3 with the shampooer. it has been awhile since i have used it and i sort of remember how to attach it but i was wondering this vacuum has a tray and i assume it is for sucking up the dirty water but when i went to use it no dirty water was going into the tray.....help what did i do wrong......thank you for your time...............spanny