The first thing you need to do is rehydrate them.  Prepare a bucket of clean, cool water (not cold).  Carefully unpack your bunches, remove the plastic wrap, and clip off the rubber bands that are binding the stems together.  Cut 1-2 centimeters off the bottom of each stem and then place the bunch in the bucket of clean water.  Be sure the water level is below the leaf line.  Allow the bunches to soak for 8 - 12 hours.  After this initial hydration period, finish unpacking the bunches by carefully removing the corrugated that is holding each bunch together.  Separate each stem and remove all the lower leaves.  Re-cut the bottom of the stem and place in a fresh, clean, bucket of water.  Your stems are ready for arranging!