This step will get the third layer side pieces into position. The next step will rotate them.
This technique will switch the positions of 3 third layer side pieces. As with the 3-side rotation, it takes a little bit of planning to be able to know which pieces to rotate. A good starting point is to find a piece that is already in position and use it as your anchor point.
With the 3 pieces you are planning to move on the top layer, and on the left, front and right positions, rotate the cube towards you 180 degrees so those pieces are on the bottom layer, and furthest from you.