License for Version Pro

Hi, I just purchased the upgrade for Catch Fullscreen Pro. I received an email saying I should input the license key following the menu Appearance => About Theme => License, but in my WordPress under Appearance there is not a voice called "About Theme", only "Theme", and under this "Theme" there is not "License". I searched everywhere but cannot find this "License" menu. So I do not know where to paste this license key in order to use the Pro version just purchased. Thank you very much for helping me further. OJ