We don't currently have an offline option for Balance.
For now, you can open any meditation and tap on the "Begin" button before you plan to be offline. This should allow all of the material to download first. For example, if your next meditation is Foundations II, Day 2, open it up while online and tap “Begin.” Once the greeting card appears, you can close it out. Later, the meditation will be playable when offline.
Alternatively, some of our meditations can be done offline and your progress will sync later when you are back online. The Breathe Single is a great one to do if you are offline and cannot download a meditation.