We are glad to know that you have received a Domestika course as a gift! At the moment, it is not possible to redeem your gift code from the app*. To do so, you should go to your profile on our website and follow the steps outlined in the following article: I've received a course as a gift, what do I have to do?
*At Domestika, we are working to implement the functionalities available on the website in each app update.