There are two ways I can think of- one is to prepare it and then put it in a ziploc bag, or better, a foodsaver bag if you have one. The other way is the way I've saved fresh spice- put it in an ice cube tray with some water, and freeze the ice cube tray. I'd do like a teaspoon per cube. When frozen, put the ice cubes in a ziploc bag.
I like the plain frozen idea better, but i've never done this with orange peel.