If you have received a voucher code for Candli, you can redeem it within Candli.
First you need to log in as a user having a free plan (available to any new user). Once logged in, you can redeem your voucher. To do so, click on your username on the left panel (1), and then click “Redeem a voucher” (2):
Then enter your code and click on “Redeem”. Note that voucher codes have the form “XXXX-XXXX-XXXX”. Candli will reload with the premium version corresponding to your voucher.