Head on over to IndieStitch.com to sign up for IndieStitch.
Select the subscription length that matches your gift voucher amount and continue through the checkout process.
In the coupon code section of the checkout, enter your gift voucher amount and this will reduce the total price by the gift voucher amount.
If you are redeeming a 6 or 12 month voucher, the total amount of the voucher will be added to your account as credit and used each month as payment until the end of the term.