Here is a simple step-by-step instruction of how to redeem your fresh promo code and get the app for free from Apple’s App Store. All you need is the promo code and your Apple ID with the password.
Find the App Store icon on your home screen and open it.
Your profile icon may look a bit different (probably your photo).
Right after you have tapped on “Redeem Gift Card or Code” you need to sign in with your Apple ID. Enter the password and proceed to step 4.
Now tap on the button “You can also enter your code manually.” and enter the promo code. Now give it a few seconds as the App Store validates your entered code.
Once you have entered promo code, the app store will automatically start to download and install the app.
When the download is complete, you can open the app.