Coupons can be applied while activating or signing up a new user, or they can be applied for an already active user.
For New Users:
1. The operator can provide the customer with the coupon code so they'd use it while signing up and subscribing to the plan they desire:
2. Or the operator can apply the coupon themselves while they're manually activating the customer's account:
For Already-Active Users:
Visit the customer account you'd like to apply the coupon for, and you'll find the option under the Plans & Billing tab:
Note: Coupons applied to an active account will apply on the next invoice/s they're issued; they will not apply to any invoices that were created before the date on which the coupon was applied to the account.