It applies to the portion of the tire that's already seated. You want to squeeze the tire on both sides and get the beads of the tire as much as possible to be in the center of the rim which is a little deeper than the edges. You need to have all the air out of the tube to do this. Just work your way around the tire and squeeze from both sides. It won't make a huge difference but it usually helps a little.

Try and use the palm of your hand to work the unseated portion of the tire over the rim a little at a time. If you use a lever or worse a screwdriver you risk pinching and puncturing the tube. Maybe try some talcum powder on the inside of the tire as well.