If you don't already have them, make a pair of doll beds with this tutorial.
Cut a piece of paper at the height you want your poles to be. Color it and cut it in fourths.
Glue each pole to the ends of the bed and fold over the top a little to create a surface to glue the top bunk. I rolled mine into cylinders, but that's entirely up to your tastes.
Put some glue on the folded tabs and attach the top bunk. Use any scrap paper to make a ladder so the dolls can climb up and down.
And you're done! The next tutorial, per Malia Hanes's request, will be for a sink and caddy with working drawers. If you have any tutorial requests, please let me know and I'll do my best to make it happen.