Mark a point on the ceiling centered above the upper third of the bed. Measure from this point to the floor. This is the length that the curtains must be.
Cut two pieces of twine, each 44 inches long. Holding them together, find the center and tie a double overhand loop knot (for instructions see: http://www.amherstlodge.com/fishing/knots/doloop/doloop.htm), leaving just enough room in the loop to fit the chandelier hook through it.
Tie the four ends of the twine pieces onto the hoop, leaving an equal amount of space between each one, and glue them in place. Make sure the center knot is in the center, otherwise the canopy will hang crookedly.
Thread the twine through one of the curtains in the space allowed for the rod. Gather it as tightly as possible, and tie it off so the twine makes a small loop through the curtain. Repeat this with the other curtains.
Hold the hook and ensure that you can hang the hoop and all curtain loops from it. Adjust as necessary, keeping the curtains on top of the hoop.
Take everything off of the hook, and place it in the ceiling at the position marked in Step 1. Be sure it is centered and secure. Hang the hoop from the hook. Next, hang the curtains from it, leaving an opening that faces the end of the bed.