One wire from the power supply goes to one of the terminal screws on the contact block. The wire going to the prop/light/ whatever you want to power goes to the other terminal screw of the contact block . If you look on the side of the contact block it should tell you if the block is N.O or N.C. The switches in the link state they are all N.O. The one with the red contact block would be suspect to me . As someone else mentioned , green contact blocks usually mean N.O. and red mean N.C. Hope this helps.
Everyone has to believe in something, I believe I'll have another beer!