Screw a small hook into the ceiling. Measure first so it's centered above your crib.
String all of the lanterns using fishing line. Use about a foot of line so you can hang some longer. It's better to have too much line and trim it after.
Hang the larger lanterns first to get the shape you'd like.
Fill in spaces rotating lanterns of different colors and patterns so the same ones aren't close together.
Trim any hanging line and check it from all angles to see if it looks balanced.