Request a refund for cancelled subscription

App: Lightroom photo and video editor

amount: $66.99

I recently discovered an unexpected charge of $66.99 before tax on my bank account, and after some investigation, I realized it was for a Lightroom photo and video editor subscription. I'm not entirely sure how this happened, but it seems that my younger brother accidentally subscribed to it. As soon as I noticed the charge, I promptly canceled the subscription. I remember reading that if it's within approximately 14 days and the service hasn't been used, a full refund may be possible according to the app's policy. I would greatly appreciate your guidance on how to initiate the refund process and resolve this matter. Thank you for your assistance in advance.