Q: How do I set up Dropbox on an iPhone/iPad?
A: go to save a deck or collection, and in the bottom left of your screen, switch from "Local" to "Dropbox". Your iPad will prompt you to set up a link with your Dropbox account if you haven't before. Afterwards, you can save any deck or collection in Dropbox. Changes to those decks or collections will be synced automatically, so you won't have to save the decks again after making changes.