Go to the app store and download Komp. Then go back to the app store, go to the Featured page, scroll to the bottom and select Redeem.
Enter your code.
Go to the Komp Store.
If the subscription does not automatically toggle, go to Check for Purchases.
If you'd like to see the subscription (not required) go to Manage Subscriptions.
Please download and be aware of the obligatory Apple Promotional Code Distribution Conditions.