For the 98 ES, I'm guessing you aready got to the slot for the filter since you said there was nothing there. The one filter that has the big plastic pieces on top goes in first. The side that says up goes up, there should be a little tab on one side, that faces you. Put that filter in the slot and slide it all the way up to the top. Take the other filter, the bigger one, and slide that one in underneath the other one. The side that says up goes up and also the tab in the middle should be facing you.