I'm glad you found your key. And thank you for the purchase.
In case someone else can't find their licence key: it is in the confirmation email sent to the address you specified in the purchase form. The key is the alphanumeric sequence between two markers:
------ KEY BEGIN KEY ------
this is the licence key
...
...
it spans over several lines
------ KEY END KEY ------
Simply copy the whole key, together with the markers, and paste it into the app. No need to type it in manually.
This article has a bit more details:
Activation: how to enter the licence key