In my setup I used 3 fans, as you can see below. The transparent fan sucks air in and pushes it towards the radiator, air passing thru the radiator is then suctioned by the 2 sandwiched fans and forces them into the case where they are sucked in by the fan on top and forced out. Remember hot air rises. I'm not quite sure why your temps are still elevated, are you sure that the direction of the airflow is from outside the case, through the fan and then to the radiator? Because I'm imagining if you installed the fan facing the wrong direction, it will bring hot air from the case towards the radiator and forced outside the case by the fan. The air that needs to hit the radiator must be cold, so yeah if the fan was installed facing the wrong way it'll make the radiator warm as warm air is being introduced to it. To check the direction of the airflow, put a piece of paper behind the rear computer case screen to see if the fan will suck it or blow it away.
to sandwich them, use 2 screws to fasten the fan and radiator to the case, then the other 2 screws to fasten the 2nd fan to the radiator, then use wiring fasteners to sandwich a third fan, the 3rd is optional as many people recommend to use only 2