Press. Press means to lay the iron on the fabric/seam.
Just like you do when you 'set' a seam. Moving the iron back and forth stretches and distorts fabric. After the quilt top is completed you can iron carefully since the all the seams will prevent stretching and distorting.
Iron is for clothes, you move the iron back and forth.
The garmet has already been sewn together so the fabric won't distort.