Here are the steps to activate your In-App Purchase upgrade with a Promo Code:
1) Open the App Store app on your iOS device.
2)
Scroll to the very bottom of the App Store and click REDEEM and wait for a pop-up menu.
3) Click on “You can also enter your code manually”.
4) Enter the PROMO CODE and click REDEEM in top right corner of your screen.
5) Sign-In Required = Enter your AppleID's password
6) Apple may ask you to agree to the latest version of their TERMS & SERVICES. - If so, click AGREE
7) Verification screen will show: "You've successfully redeemed your code"
At this point your upgrade is almost complete. Click DONE in the top right corner of your screen.
8) Open your app and click where it says UPGRADE TO PREMIUM VERSION or UPGRADE TO PRO VERSION. See the screenshot attached below for additional reference.
9) Click the RESTORE button to upgrade your app.
At this point, your app should now say Property Evaluator Pro along the top of the screen and your upgrade is complete.