Get There: Setup > Manage Programs
Find the program your rewards are attached to. Select the Edit icon.
Scroll down and click Next to go to the badges page.
Under the registration badge, you'll see the option to Add or Edit Rewards. Find the reward/prize you wish to edit and click Edit Selected Reward.
For other types of badges, you will need to click on the name of the badge, and then scroll down past all badge images until you see the reward. Then, you may select a different reward or "edit selected reward."
Update the name or instructions as needed.
Remember to save this change AND to save the program before you exit.
NOTE: Use caution when updating prize details, as any updates will affect the prize everywhere it is attached.