The Pilot’s Book · Growing stronger
Promo codes
«Settings» → «Promo code» → «Enter»: type the code and press «Activate».
Open «Settings» (the menu «⋯» or the captain's menu) and press «Enter» by «Promo code». 
Type the code into the field and press «Activate». Letters may be in any case. 
The answer is right under it: what you got, or why the code did not fit (spent, expired, not for your level). Each code works once a captain; codes for newcomers work up to level 15.
